Coordinate Geometry

ICSE Class 9 Mathematics · ML Aggarwal Solutions Understanding ICSE Mathematics Class 9 · 118 solved questions

Exercise
Marks
1Exercise 18.1

Find the coordinates of points whose

(i) abscissa is 3 and ordinate -4.

(ii) abscissa is $-\frac{3}{2}$ and ordinate 5.

(iii) whose abscissa is $-1\frac{2}{3}$ and ordinate $-2\frac{1}{4}$.

(iv) whose ordinate is 5 and abscissa is -2.

(v) whose abscissa is -2 and lies on x-axis.

(vi) whose ordinate is $\frac{3}{2}$ and lies on y-axis.

Show SolutionHide Solution↓

We know that,

Abscissa is the x-coordinate and ordinate is the y-coordinate of a point.

(i) The coordinate of the point whose abscissa is 3 and ordinate is -4 is (3, -4).

(ii) The coordinate of the point whose abscissa is $-\frac{3}{2}$ and ordinate is 5 is $\Big(-\frac{3}{2}, 5)$.

(iii) The coordinate of the point whose whose abscissa is $-1\frac{2}{3}$ and ordinate $-2\frac{1}{4}$ is $\Big(-1\frac{2}{3}, -2\frac{1}{4}\Big)$.

(iv) The coordinate of the point whose ordinate is 5 and abscissa is -2 is (-2, 5).

(v) Since, point lies on x-axis. So, ordinate of point will be = 0.

The coordinate of the point whose abscissa is -2 and lies on x-axis is (-2,0).

(vi) Since, point lies on y-axis. So, abscissa of point will be = 0.

The coordinate of the point whose ordinate is $\frac{3}{2}$ and lies on y-axis is $\Big(0, \frac{3}{2}\Big)$.

2Exercise 18.1

In which quadrant or on which axis each of the following points lie?

(-3, 5), (4, -1) (2, 0), (2, 2), (-3, -6)

Show SolutionHide Solution↓

From figure,

In which quadrant or on which axis each of the following points lie? (-3, 5), (4, -1) (2, 0), (2, 2), (-3, -6). Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

(-3, 5) lies in second quadrant.

(4, -1) lies in fourth quadrant.

(2, 0) lies on x-axis.

(2, 2) lies in first quadrant.

(-3, -6) lies in third quadrant.

3Exercise 18.1

Which of the following points lie on (i) x-axis? (ii) y-axis?

A(0, 2), B(5, 6), C(23, 0), D(0, 23), E(0, -4), F(-6, 0), G ($\sqrt{3}$,0).

Show SolutionHide Solution↓

Given points are A (0, 2), B (5, 6), C (23, 0), D (0, 23), E (0, -4), F (-6, 0), G ($\sqrt{3}$,0)

(i) If y-coordinate of a point is zero, then the point lies on x-axis.

Hence, C(23, 0), F(-6, 0) and G($\sqrt{3}$, 0) lies on x-axis.

(ii) If x-coordinate of a point is zero, then the point lies on y-axis.

Hence, A(0, 2), D(0, 23) and E(0, -4) lies on y-axis.

4Exercise 18.1

Plot the following points on the graph paper :

A(3, 4), B(-3, 1), C(1, -2), D(-2, -3), E(0, 5), F(5, 0), G(0, -3), H(-3, 0).

Show SolutionHide Solution↓

The points are shown in the below graph:

Plot the following points on the graph paper : A(3, 4), B(-3, 1), C(1, -2), D(-2, -3), E(0, 5), F(5, 0), G(0, -3), H(-3, 0). Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.
5Exercise 18.1

Write the co-ordinates of the points A, B, C, D, E, F, G and H shown in the adjacent figure.

Write the co-ordinates of the points A, B, C, D, E, F, G and H shown in the adjacent figure. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.
Show SolutionHide Solution↓

From figure,

The co-ordinates of the points are:

PointCo-ordinates
A(2, 2)
B(-3, 0)
C(-2, -4)
D(3, -1)
E(-4, 4)
F(0, -2)
G(2, -3)
H(0, 3)
6Exercise 18.1

In which quadrants are the points A, B, C and D of problem 5 located ?

Show SolutionHide Solution↓

In point A(2, 2), both x and y coordinates are positive. So it lies in the first quadrant.

In point B(-3, 0), y-coordinate is zero. So it lies on x-axis.

In point C(-2, -4), both x and y coordinates are negative. So it lies in the third quadrant.

In point D(3, -1), x coordinate is positive and y coordinate is negative. So it lies in the fourth quadrant.

7Exercise 18.1

Plot the following points on the same graph paper :

$A\Big(2, \frac{5}{2}\Big), B\Big(-\frac{3}{2}, 3\Big), C\Big(\frac{1}{2}, -\frac{3}{2}\Big)\text{ and } D\Big(-\frac{5}{2}, -\frac{1}{2}\Big).$

Show SolutionHide Solution↓

The points are shown on the graph below:

Plot the following points on the same graph paper : A(2, 5/2), B(-3/2, 3), C(1/2, -3/2) and D(-5/2, -1/2). Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.
8Exercise 18.1

Plot the following points on the same graph paper.

$A\Big(\frac{4}{3}, -1\Big), B\Big(\frac{7}{2}, \frac{5}{3}\Big), C\Big(\frac{13}{6}, 0\Big)\text{ and } D\Big(-\frac{5}{3}, -\frac{5}{2}\Big).$

Show SolutionHide Solution↓

The points are shown on the graph below:

Plot the following points on the same graph paper. A(4/3, -1), B(7/2, 5/3), C(13/6, 0) and  D(-5/3, -5/2). Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.
9Exercise 18.1

Plot the following points and check whether they are collinear or not :

(i) (1, 3), (-1, -1) and (-2, -3)

(ii) (1, 2), (2, -1) and (-1, 4)

(iii) (0, 1), (2, -2) and $(\frac{2}{3} ,0)$.

Show SolutionHide Solution↓

(i)

Plot the following points and check whether they are collinear or not : (i) (1, 3), (-1, -1) and (-2, -3). Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Points (1, 3), (-1, -1) and (-2, -3) lie on a straight line, so they are collinear.

(ii)

Plot the following points and check whether they are collinear or not : (ii) (1, 2), (2, -1) and (-1, 4). Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Points (1, 2), (2, -1) and (-1, 4) do not lie on a line. So they are non-collinear.

(iii)

Plot the following points and check whether they are collinear or not : (iii) (0, 1), (2, -2) and (2/3 ,0). Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Points (0, 1), (2, -2) and $(\frac{2}{3} ,0)$ lie on a straight line, so they are collinear.

10Exercise 18.1

Plot the point P(-3, 4). Draw PM and PN perpendiculars to x-axis and y-axis respectively. State the co-ordinates of the points M and N.

Show SolutionHide Solution↓

The points are shown on the graph below:

Plot the point P(-3, 4). Draw PM and PN perpendiculars to x-axis and y-axis respectively. State the co-ordinates of the points M and N. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Steps of construction :

  1. Plot point P(-3, 4) on graph.

  2. Draw PM and PN which are perpendiculars to x-axis and y-axis respectively.

From figure,

Coordinates of point M = (-3, 0) and N = (0, 4).

11Exercise 18.1

Plot the points A(1, 2), B(-4, 2), C(-4, -1) and D (1, -1). What kind of quadrilateral is ABCD? Also find the area of the quadrilateral ABCD.

Show SolutionHide Solution↓

The points are shown on the graph below:

Plot the points A(1, 2), B(-4, 2), C(-4, -1) and D (1, -1). What kind of quadrilateral is ABCD? Also find the area of the quadrilateral ABCD. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Steps of construction :

  1. Plot the points A (1, 2), B (-4, 2), C (-4, -1) and D (1, -1) on graph.

  2. Join AB, BC, CD and AD.

From graph,

ABCD is a rectangle.

1 block = 1 unit

AB = 5 units, AD = 3 units

Area of rectangle ABCD = length × breadth

= AB × AD

= 5 × 3

= 15 sq. units.

Hence, ABCD is a rectangle and its area = 15 sq. units.

12Exercise 18.1

Plot the points (0, 2), (3, 0), (0, -2) and (-3, 0) on a graph paper. Join these points (in order). Name the figure so obtained and find the area of the figure obtained.

Show SolutionHide Solution↓

The points are shown on the graph below:

Plot the points (0, 2), (3, 0), (0, -2) and (-3, 0) on a graph paper. Join these points (in order). Name the figure so obtained and find the area of the figure obtained. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Steps of construction :

  1. Plot the points A(0, 2), B(3, 0), C(0, -2) and D(-3,0) on graph.

  2. Join AB, BC, CD and DA. ABCD is a rhombus.

  3. Join BD and AC.

BD and AC are the diagonals of the rhombus.

Area of a rhombus = $\frac{1}{2}$ × d1 × d2

From graph,

1 block = 1 unit.

AC = 4 units

BD = 6 units.

Area of rhombus ABCD = $\frac{1}{2}$ × BD × AC

= $\frac{1}{2}$ × 6 × 4

= 12 sq. units.

Hence, figure obtained form graph is a rhombus with area = 12 sq. units.

13Exercise 18.1

Three vertices of a square are A(2, 3), B (-3, 3) and C (-3, -2). Plot these points on a graph paper and hence use it to find the co-ordinates of the fourth vertex. Also find the area of the square.

Show SolutionHide Solution↓

The points are shown on the graph below:

Three vertices of a square are A(2, 3), B (-3, 3) and C (-3, -2). Plot these points on a graph paper and hence use it to find the co-ordinates of the fourth vertex. Also find the area of the square. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Steps of construction :

  1. Plot points A(2, 3), B(-3, 3) and C(-3, -2) on graph.

  2. Measure AB.

  3. Mark point D such that it is at a distance AB from points A and C.

  4. Join AB, BC, CD and DA.

On measuring,

AB = 5 units [As, 1 block = 1 unit]

Area of the square = side × side

Area of the square ABCD = AB × AB

= 5 × 5 = 25 sq. units.

Hence, the coordinates of D = (2, -2) and area of the square is 25 sq. units.

14Exercise 18.1

Write the co-ordinates of the vertices of a rectangle which is 6 units long and 4 units wide if the rectangle is in the first quadrant, its longer side lies on the x-axis and one vertex is at the origin.

Show SolutionHide Solution↓

The points are shown on the graph below:

Write the co-ordinates of the vertices of a rectangle which is 6 units long and 4 units wide if the rectangle is in the first quadrant, its longer side lies on the x-axis and one vertex is at the origin. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Given,

The rectangle which is 6 units long and 4 units wide is shown in the graph.

Rectangle is in the first quadrant.

Longer side lies on x-axis and one vertex is at origin A(0, 0).

Steps of construction :

  1. Mark point A(0, 0).

  2. At a distance of 6 units on x-axis mark point B(6, 0).

  3. From B draw a line segment parallel to y-axis and mark point C on it at distance of 4 units.

  4. From C draw a line segment parallel to x-axis and mark point D on it at distance of 6 units.

  5. Join DA.

Hence, coordinates of the rectangle are A(0, 0), B(6, 0), C(6, 4) and D(0, 4).

15Exercise 18.1

In the adjoining figure, ABCD is a rectangle with length 6 units and breadth 3 units. If O is the mid-point of AB, find the coordinates of A, B, C and D.

In the adjoining figure, ABCD is a rectangle with length 6 units and breadth 3 units. If O is the mid-point of AB, find the coordinates of A, B, C and D. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.
Show SolutionHide Solution↓

Given,

Length = 6 units.

Breadth = 3 units

AB = 6 units.

As, 1 block = 1 unit

From graph,

In the adjoining figure, ABCD is a rectangle with length 6 units and breadth 3 units. If O is the mid-point of AB, find the coordinates of A, B, C and D. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

A = (-3, 0)

B = (3, 0)

C = (3, 3)

D = (-3, 3).

16Exercise 18.1

The adjoining figure shows an equilateral triangle OAB with each side = 2a units. Find the coordinates of the vertices.

The adjoining figure shows an equilateral triangle OAB with each side = 2a units. Find the coordinates of the vertices. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.
Show SolutionHide Solution↓

Given equilateral triangle OAB.

OA = OB = AB = 2a units.

Draw AD ⊥ OB.

The adjoining figure shows an equilateral triangle OAB with each side = 2a units. Find the coordinates of the vertices. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

In an equilateral triangle, a perpendicular drawn from one of the vertices to the opposite side bisects the side.

∴ OD = $\frac{1}{2}$ x OB = $\frac{1}{2}$ x 2a = a.

In right angle triangle OAD,

⇒ OA2 = OD2 + AD2

⇒ (2a)2 = a2 + AD2

⇒ 4a2 = a2 + AD2

⇒ AD2 = 4a2 - a2

⇒ AD2 = 3a2

⇒ AD = $\sqrt{3a}$ units.

⇒ AD = $\sqrt{3}$a units.

From graph,

Co-ordinates of O = (0, 0)

Co-ordinates of B = (2a, 0)

As, OD = a units and AD = $\sqrt{3}$a units.

Co-ordinates of A = (a, $\sqrt{3}$a).

Hence, co-ordinates of O = (0, 0), B = (2a, 0) and A = (a, $\sqrt{3}$a).

17Exercise 18.1

In the given figure, △PQR is equilateral. If the coordinates of the points Q and R are (0, 2) and (0, -2) respectively, find the coordinates of the point P.

In the given figure, △PQR is equilateral. If the coordinates of the points Q and R are (0, 2) and (0, -2) respectively, find the coordinates of the point P. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.
Show SolutionHide Solution↓

Given, PQR is an equilateral triangle in which Q(0, 2) and R(0, -2) and O = (0, 0).

Let (x, 0) be the coordinates of P. [As, P lies on x axis, so y-coordinate is zero.]

By distance formula,

$$\begin{aligned}\Rightarrow QR = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] = \sqrt{(0 - 0)^2 + (-2 - 2)^2} \\[1em] = \sqrt{0 + (-4)^2} \\[1em] = \sqrt{16} \\[1em] = 4 \text{ units}. \\[1em] \Rightarrow OQ = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] = \sqrt{(0 - 0)^2 + (2 - 0)^2} \\[1em] = \sqrt{0 + (2)^2} \\[1em] = \sqrt{4} \\[1em] = 2 \text{ units}.\end{aligned}$$

PQ = PR = QR = 4.

OQ = 2

In right angle triangle POQ,

⇒ PQ2 = OP2 + OQ2 [By pythagoras theorem]

⇒ 42 = OP2 + 22

⇒ 16 = OP2 + 4

⇒ OP2 = 16 - 4

⇒ OP2 = 12

⇒ OP = $\sqrt{12} = 2\sqrt{3}$.

Since, P lies on x-axis and OP = $2\sqrt{3}$.

Hence, the coordinates of P are ($2\sqrt{3}$, 0).

1(i)Exercise 18.2

Draw the graph of the following linear equation :

2x + y + 3 = 0

Show SolutionHide Solution↓

The given equation 2x + y + 3 = 0, can be written as :

⇒ y = -2x - 3

When x = 0, y = -2(0) - 3 = -3,

x = 1, y = -2(1) - 3 = -2 - 3 = -5,

x = 2, y = -2(2) - 3 = -4 - 3 = -7.

Table of values :

xy
0-3
1-5
2-7

Steps of construction :

  1. Plot the points (0, -3), (1, -5) and (2, -7) on the graph.

  2. Connect any two points by a straight line.

Observe that the third point lies on the straight line.

Draw the graph of the following linear equation : 2x + y + 3 = 0. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Hence, the graph of the given equation is shown in the adjoining figure.

1(ii)Exercise 18.2

Draw the graph of the following linear equation :

x - 5y - 4 = 0

Show SolutionHide Solution↓

The given equation x - 5y - 4 = 0, can be written as :

⇒ 5y = x - 4

⇒ y = $\frac{1}{5}$(x - 4)

When x = -6, y = $\frac{1}{5}(-6 - 4) = -\frac{10}{5}$ = -2,

x = -1, y = $\frac{1}{5}(-1 - 4) = -\frac{5}{5}$ = -1,

x = 4, y = $\frac{1}{5}(4 - 4) = \frac{0}{5}$ = 0.

Table of values :

xy
-6-2
-1-1
40

Steps of construction :

  1. Plot the points (-6, -2), (-1, -1) and (4, 0) on the graph.

  2. Connect any two points by a straight line.

Observe that the third point lies on the straight line.

Draw the graph of the following linear equation : x - 5y - 4 = 0. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Hence, the graph of the given equation is shown in the adjoining figure.

2Exercise 18.2

Draw the graph of 3y = 12 - 2x. Take 2 cm = 1 unit on both axes.

Show SolutionHide Solution↓

The above equation, 3y = 12 - 2x can be written as :

⇒ 3y = 12 - 2x

⇒ y = $\frac{12}{3} - \frac{2x}{3}$

⇒ y = 4 - $\frac{2x}{3}$.

When x = -3, y = 4 - $\frac{(2 \times -3)}{3} = 4 - \frac{-6}{3}$ = 4 - (-2) = 6,

x = 0, y = 4 - $\frac{2 \times 0}{3} = 4 - 0$ = 4,

x = 3, y = 4 - $\frac{2 \times 3}{3}$ = 4 - 2 = 2.

Table of values :

xy
-36
04
32

Steps of construction :

  1. Plot the points (-3, 6), (0, 4) and (3, 2) on the graph.

  2. Connect any two points by a straight line.

Observe that the third point lies on the straight line.

Draw the graph of 3y = 12 - 2x. Take 2 cm = 1 unit on both axes. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Hence, the graph of the given equation is shown in the adjoining figure.

3Exercise 18.2

Draw the graph of 5x + 6y - 30 = 0 and use it to find the area of the triangle formed by the line and coordinate axes.

Show SolutionHide Solution↓

The above equation, 5x + 6y - 30 = 0 can be written as :

⇒ 6y = -5x + 30

⇒ y = $\frac{1}{6}(-5x + 30)$

⇒ y = $-\frac{5x}{6} + 5$.

When x = 0, y = -$\frac{(5 \times 0)}{6} + 5$ = 0 + 5 = 5,

x = 6, y = -$\frac{5 \times 6}{6} + 5$ = -5 + 5 = 0,

x = 12, y = -$\frac{5 \times 12}{6}$ + 5 = -10 + 5 = -5.

Table of values :

xy
05
60
12-5

Steps of construction :

  1. Plot the points (0, 5), (6, 0) and (12, -5) on the graph.

  2. Connect any two points by a straight line.

Observe that the third point lies on the straight line.

Draw the graph of 5x + 6y - 30 = 0 and use it to find the area of the triangle formed by the line and coordinate axes. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By formula,

Area of triangle = $\frac{1}{2} \times \text{ base} \times \text{ height}$

From graph,

Base = 6 units, Height = 5 units.

Area = $\frac{1}{2} \times 6 \times 5 = 15$ sq. units.

Hence, the graph of the given equation is shown in the adjoining figure and area of triangle = 15 sq. units.

4Exercise 18.2

Draw the graph of 4x - 3y + 12 = 0 and use it to find the area of the triangle formed by the line and co-ordinate axes. Take 2 cm = 1 unit on both axes.

Show SolutionHide Solution↓

The above equation, 4x - 3y + 12 = 0 can be written as :

⇒ 3y = 4x + 12

⇒ y = $\frac{4}{3}x + 4$

When x = -6, y = $\frac{4}{3} \times -6 + 4$ = -8 + 4 = -4,

x = -3, y = $\frac{4}{3} \times -3 + 4 =$ -4 + 4 = 0,

x = 0, y = $\frac{4}{3} \times 0 + 4 =$ 0 + 4 = 4.

Table of values :

xy
-6-4
-30
04

Steps of construction :

  1. Plot the points (-6, -4), (-3, 0) and (0, 4) on the graph.

  2. Connect any two points by a straight line.

Observe that the third point lies on the straight line.

Draw the graph of 4x - 3y + 12 = 0 and use it to find the area of the triangle formed by the line and co-ordinate axes. Take 2 cm = 1 unit on both axes. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By formula,

Area of triangle = $\frac{1}{2} \times \text{ base} \times \text{ height}$

From graph,

Base = 3 units, Height = 4 units.

Area = $\frac{1}{2} \times 3 \times 4 = 6$ sq. units.

Hence, the graph of the given equation is shown in the adjoining figure and area of triangle = 6 sq. units.

5Exercise 18.2

Draw the graph of the equation y = 3x - 4. Find graphically

(i) the value of y when x = -1

(ii) the value of x when y = 5.

Show SolutionHide Solution↓

Equation :

⇒ y = 3x - 4

When x = 0, y = 3(0) - 4 = 0 - 4 = -4,

x = 2, y = 3(2) - 4 = 6 - 4 = 2,

Table of values :

xy
0-4
22

Steps of construction :

  1. Plot the points (0, -4) and (2, 2) on the graph.

  2. Connect the two points by a straight line.

Hence, the graph of the given equation is shown in the adjoining figure.

(i) Steps of construction :

  1. From point, P (x = -1) draw a line parallel to y-axis touching the graph. Mark the point as Q.

  2. From Q draw a line parallel to x-axis, touching y-axis at point R (y = -7).

Hence, y = -7, when x = -1.

(ii) Steps of construction :

  1. From point, S (y = 5) draw a line parallel to x-axis touching the graph. Mark the point as T.

  2. From T draw a line parallel to y-axis, touching x-axis at point U (x = 3).

Draw the graph of the equation y = 3x - 4. Find graphically. (i) the value of y when x = -1 (ii) the value of x when y = 5.  Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Hence, x = 3, when y = 5.

6Exercise 18.2

The graph of a linear equation in x and y passes through (4, 0) and (0, 3). Find the value of k if the graph passes through (k, 1.5).

Show SolutionHide Solution↓

Steps of construction :

  1. Plot the points (4, 0) and (0, 3) on graph.

  2. Connect the points through a straight line.

  3. Take a point Q (y = 1.5) and draw a line parallel to x-axis touching the graph at point R.

  4. From point R draw a line parallel to y-axis and touching x-axis at point S (x = 2).

The graph of a linear equation in x and y passes through (4, 0) and (0, 3). Find the value of k if the graph passes through (k, 1.5). Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph R = (2, 1.5)

Comparing point R with (k, 1.5), we get :

k = 2.

Hence, the value of k = 2.

7Exercise 18.2

Use the table given alongside to draw the graph of a straight line. Find, graphically, the values of a and b.

x123a
y-2b4-5
Show SolutionHide Solution↓

Steps of construction :

  1. Plot the points (1, -2) and (3, 4) on graph paper.

  2. Connect the points through a straight line.

  3. Take a point C (x = 2) and draw a line parallel to y-axis touching the graph at point B.

  4. From point B draw a line parallel to x-axis and touching y-axis at point A (y = 1).

Use the table given alongside to draw the graph of a straight line. Find, graphically, the values of a and b. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

B = (2, 1)

Comparing it with (2, b) we get :

b = 1.

Also, the graph touches y-axis at (0, -5).

Comparing it with (a, -5) we get :

a = 0.

Hence, a = 0 and b = 1.

1Exercise 18.3

Solve the following equations graphically :

3x - 2y = 4, 5x - 2y = 0.

Show SolutionHide Solution↓

Given,

Equation :

⇒ 3x - 2y = 4

⇒ 2y = 3x - 4

⇒ y = $\frac{3}{2}$x - 2 .........(1)

When, x = -2, y = $\frac{3}{2} \times -2 - 2$ = -3 - 2 = -5,

x = 0, y = $\frac{3}{2} \times 0 - 2$ = 0 - 2 = -2,

x = 2, y = $\frac{3}{2} \times 2 - 2$ = 3 - 2 = 1.

Tables of values for equation (1)

x-202
y-5-21

Steps of construction :

  1. Plot the points (-2, -5), (0, -2) and (2, 1) on graph paper.

  2. Connect points by straight line.

Given,

Equation :

⇒ 5x - 2y = 0

⇒ 2y = 5x

⇒ y = $\frac{5}{2}x$ ..............(2)

When, x = -2, y = $\frac{5}{2} \times -2$ = -5,

x = 0, y = $\frac{5}{2} \times 0$ = 0,

x = 2, y = $\frac{5}{2} \times 2$ = 5.

Tables of values for equation (2)

x-202
y-505

Steps of construction :

  1. Plot the points (-2, -5), (0, 0) and (2, 5) on graph paper.

  2. Connect points by straight line.

The graphs of both the straight lines are shown in the figure.

Solve the following equations graphically : 3x - 2y = 4, 5x - 2y = 0. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

The lines intersect at point A(-2, -5).

Hence, the solution of the given equations is x = -2, y = -5.

2Exercise 18.3

Solve the following pair of equations graphically. Plot atleast 3 points for each straight line.

2x - 7y = 6, 5x - 8y = -4.

Show SolutionHide Solution↓

Given,

Equation :

⇒ 2x - 7y = 6

⇒ 2x = 6 + 7y

⇒ x = $\frac{6 + 7y}{2}$ ..........(1)

When y = 0, x = $\frac{6 + 7 \times 0}{2} = \frac{6}{2}$ = 3,

y = -1, x = $\frac{6 + 7 \times -1}{2} = \frac{6 - 7}{2}$ = -0.5,

y = -2, x = $\frac{6 + 7 \times -2}{2} = \frac{6 - 14}{2} = -\frac{8}{2}$ = -4.

Table of values for equation (1)

x3-0.5-4
y0-1-2

Steps of construction :

  1. Plot the points (3, 0), $(-\frac{1}{2}, -1)$ and (-4, -2) on graph paper.

  2. Connect points by straight line.

Given,

Equation :

⇒ 5x - 8y = -4

⇒ 5x = 8y - 4

⇒ x = $\frac{8}{5}$y - $\frac{4}{5}$ ..............(2)

When, y = 0, x = $\frac{8}{5} \times 0 - \frac{4}{5} = 0 - \frac{4}{5} =$ -0.8,

y = 3, x = $\frac{8}{5} \times 3 - \frac{4}{5} = \frac{24}{5} - \frac{4}{5} = \frac{20}{5}$ = 4,

y = -2, x = $\frac{8}{5} \times -2 - \frac{4}{5} = -\frac{16}{5} - \frac{4}{5} = -\frac{20}{5}$ = -4.

Table of values for equation (2)

x-0.84-4
y03-2

Steps of construction :

  1. Plot the points (-0.8, 0), (4, 3) and (-4, -2) on graph paper.

  2. Connect points by straight line.

The graphs of both the straight lines are shown in the figure.

Solve the following pair of equations graphically. Plot atleast 3 points for each straight line. 2x - 7y = 6, 5x - 8y = -4. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

The lines intersect at point A(-4, -2).

Hence, the solution of the given equations is x = -4, y = -2.

3Exercise 18.3

Using the same axes of coordinates and the same unit, solve graphically.

x + y = 0, 3x - 2y = 10.

Show SolutionHide Solution↓

Given,

Equation :

⇒ x + y = 0

⇒ y = -x .............(1)

When, x = 0, y = 0,

x = 1, y = -(1) = -1,

x = 2, y = -(2) = -2.

Table of values for equation (1)

x012
y0-1-2

Steps of construction :

  1. Plot the points (0, 0), (1, -1) and (2, -2) on graph paper.

  2. Connect points by straight line.

Given,

Equation :

⇒ 3x - 2y = 10

⇒ 2y = 3x - 10

⇒ y = $\frac{3}{2}x - 5$ ............(2)

When, x = 0, y = $\frac{3}{2} \times 0 - 5$ = 0 - 5 = -5,

x = 2, $y = \frac{3}{2} \times 2 - 5$ = 3 - 5 = -2,

x = 4, $y = \frac{3}{2} \times 4 - 5$ = 6 - 5 = 1.

Table of values for equation (2)

x024
y-5-21

Steps of construction :

  1. Plot the points (0, -5), (2, -2) and (4, 1) on graph paper.

  2. Connect points by straight line.

The graphs of both the straight lines are shown in the figure.

Using the same axes of coordinates and the same unit, solve graphically. x + y = 0, 3x - 2y = 10. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

The lines intersect at point A(2, -2).

Hence, the solution of the given equations is x = 2, y = -2.

4Exercise 18.3

Take 1 cm to represent 1 unit on each axis to draw the graphs of the equations 4x - 5y = -4 and 3x = 2y - 3 on the same graph sheet (same axes). Use your graph to find the solution of the above simultaneous equations.

Show SolutionHide Solution↓

Given,

Equation :

⇒ 4x - 5y = -4

⇒ 5y = 4x + 4

⇒ y = $\frac{4x + 4}{5}$.............(1)

When, x = -1, y = $\frac{4 \times -1 + 4}{5} = \frac{0}{5}$ = 0,

x = 1.5, y = $\frac{4 \times 1.5 + 4}{5} = \frac{10}{5}$ = 2,

x = 4, y = $\frac{4 \times 4 + 4}{5} =\frac{20}{5}$ = 4.

Table of values for equation (1)

x-11.54
y024

Steps of construction :

  1. Plot the points (-1, 0), (1.5, 2) and (4, 4) on graph paper.

  2. Connect points by straight line.

Given,

Equation :

⇒ 3x = 2y - 3

⇒ 2y = 3x + 3

⇒ y = $\frac{3x + 3}{2}$ ............(2)

When, x = -1, y = $\frac{3 \times -1 + 3}{2} = \frac{-3 + 3}{2} = \frac{0}{2}$ = 0,

x = 0, $y = \frac{3 \times 0 + 3}{2} = \frac{3}{2}$ = 1.5,

x = 1, $y = \frac{3 \times 1 + 3}{2} = \frac{6}{2}$ = 3.

Table of values for equation (2)

x-101
y01.53

Steps of construction :

  1. Plot the points (-1, 0), (0, 1.5) and (1, 3) on graph paper.

  2. Connect points by straight line.

The graphs of both the straight lines are shown in the figure.

Take 1 cm to represent 1 unit on each axis to draw the graphs of the equations 4x - 5y = -4 and 3x = 2y - 3 on the same graph sheet (same axes). Use your graph to find the solution of the above simultaneous equations. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

The lines intersect at point A(-1, 0).

Hence, the solution of the given equations is x = -1, y = 0.

5Exercise 18.3

Solve the following simultaneous equations graphically :

x + 3y = 8, 3x = 2 + 2y.

Show SolutionHide Solution↓

Given,

Equation :

x + 3y = 8

x = 8 - 3y ..........(1)

When, y = 1, x = 8 - 3(1) = 8 - 3 = 5,

y = 2, x = 8 - 3(2) = 8 - 6 = 2,

y = 3, x = 8 - 3(3) = 8 - 9 = -1.

Table of values for equation (1)

x-125
y321

Steps of construction :

  1. Plot the points (-1, 3), (2, 2) and (5, 1) on graph paper.

  2. Connect points by straight line.

Given,

Equation :

⇒ 3x = 2 + 2y

⇒ x = $\frac{2 + 2y}{3}$ ..........(2)

When, y = -1, x = $\frac{2 + 2 \times -1}{3} = \frac{2 - 2}{3}$ = 0.

y = 2, x = $\frac{2 + 2 \times 2}{3} = \frac{6}{3}$ = 2,

y = 5, x = $\frac{2 + 2 \times 5}{3} = \frac{12}{3}$ = 4.

Table of values for equation (2)

x024
y-125

Steps of construction :

  1. Plot the points (0, -1), (2, 2) and (4, 5) on graph paper.

  2. Connect points by straight line.

The graphs of both the straight lines are shown in the figure.

Solve the following simultaneous equations graphically : x + 3y = 8, 3x = 2 + 2y. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

The lines intersect at point A(2, 2).

Hence, the solution of the given equations is x = 2, y = 2..

6Exercise 18.3

Solve graphically the simultaneous equations 3y = 5 - x, 2x = y + 3.

Show SolutionHide Solution↓

Given,

⇒ 3y = 5 - x

⇒ y = $\frac{5 - x}{3}$ .......(1)

When x = -4, y = $\frac{5 - (-4)}{3} = \frac{9}{3}$ = 3,

x = -1, y = $\frac{5 - (-1)}{3} = \frac{6}{3}$ = 2,

x = 2, y = $\frac{5 - 2}{3} = \frac{3}{3}$ = 1.

Table of values for equation (1)

x-4-12
y321

Steps of construction :

  1. Plot the points (-4, 3), (-1, 2) and (2, 1) on graph paper.

  2. Connect points by straight line.

Given,

⇒ 2x = y + 3

⇒ y = 2x - 3 ...........(2)

When x = 0, y = 2 × 0 - 3 = 0 - 3 = -3,

x = 1, y = 2 × 1 - 3 = 2 - 3 = -1,

x = 2, y = 2 × 2 - 3 = 4 - 3 = 1.

Table of values for equation (2)

x012
y-3-11

Steps of construction :

  1. Plot the points (0, -3), (1, -1) and (2, 1) on graph paper.

  2. Connect points by straight line.

From graph,

Solve graphically the simultaneous equations 3y = 5 - x, 2x = y + 3. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

The two lines meet at point P(2, 1).

Hence, the solution of the given equations is x = 2, y = 1.

7Exercise 18.3

Use graph paper for this question. Take 2 cm = 1 unit on both axes.

(i) Draw the graphs of x + y + 3 = 0 and 3x - 2y + 4 = 0. Plot three points per line.

(ii) Write down the coordinates of the point of intersection of the lines.

(iii) Measure and record the distance of the point of intersection of the lines from the origin in cm.

Show SolutionHide Solution↓

(i) Given,

⇒ x + y + 3 = 0

⇒ y = -(3 + x) .........(1)

When x = -1, y = -[3 + (-1)] = -(3 - 1) = -2,

x = 0, y = -(3 + 0) = -3,

x = 1, y = -(3 + 1) = -4.

Table of values for equation (1)

x-101
y-2-3-4

Steps of construction :

  1. Plot the points (-1, -2), (0, -3) and (1, -4) on graph paper.

  2. Connect points by straight line.

Given,

⇒ 3x - 2y + 4 = 0

⇒ 2y = 3x + 4

⇒ y = $\frac{3x + 4}{2}$

When x = -2, y = $\frac{3 \times -2 + 4}{2} = \frac{-6 + 4}{2} = \frac{-2}{2}$ = -1,

x = 0, y = $\frac{3 \times 0 + 4}{2} = \frac{4}{2}$ = 2,

x = 2, y = $\frac{3 \times 2 + 4}{2} = \frac{6 + 4}{2} = \frac{10}{2}$ = 5.

Table of values for equation (2)

x-202
y-125

Steps of construction :

  1. Plot the points (-2, -1), (0, 2) and (2, 5) on graph paper.

  2. Connect points by straight line.

Use graph paper for this question. Take 2 cm = 1 unit on both axes. (i) Draw the graphs of x + y + 3 = 0 and 3x - 2y + 4 = 0. Plot three points per line. (ii) Write down the coordinates of the point of intersection of the lines. (iii) Measure and record the distance of the point of intersection of the lines from the origin in cm. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

(ii) From graph,

P(-2, -1) is the intersection of lines.

Hence, coordinates of point of intersection = (-2, -1).

(iii) From P, draw a perpendicular to y-axis.

As, 1 unit = 2 cm.

So, PQ = 2 unit = 4 cm, OQ = 1 unit = 2 cm.

In right angle triangle,

By pythagoras theorem,

⇒ OP2 = PQ2 + OQ2

⇒ OP2 = 42 + 22

⇒ OP2 = 16 + 4

⇒ OP2 = 20

⇒ OP = $\sqrt{20}$ = 4.5 cm

Hence, distance of the point of intersection of the lines from the origin = 4.5 cm.

8Exercise 18.3

Solve the following simultaneous equations, graphically :

2x - 3y + 2 = 4x + 1 = 3x - y + 2.

Show SolutionHide Solution↓

Considering,

⇒ 2x - 3y + 2 = 4x + 1

⇒ 3y = 2x - 4x + 2 - 1

⇒ 3y = -2x + 1

⇒ y = $\frac{1 - 2x}{3}$ .........(1)

When, x = -4, y = $\frac{1 - 2 \times (-4)}{3} = \frac{1 + 8}{3} = \frac{9}{3}$ = 3,

x = -1, y = $\frac{1 - 2 \times (-1)}{3} = \frac{1 + 2}{3} = \frac{3}{3}$ = 1,

x = 2, y = $\frac{1 - 2 \times 2}{3} = \frac{1 - 4}{3} = \frac{-3}{3}$ = -1.

Table of values for equation (1)

x-4-12
y31-1

Steps of construction :

  1. Plot the points (-4, 3), (-1, 1) and (2, -1) on graph paper.

  2. Connect points by straight line.

Considering,

⇒ 4x + 1 = 3x - y + 2

⇒ y = 3x - 4x + 2 - 1

⇒ y = -x + 1

⇒ y = 1 - x ............(2)

When, x = 0, y = 1 - 0 = 1,

x = 1, y = 1 - 1 = 0,

x = 2, y = 1 - 2 = -1.

Table of values for equation (2)

x012
y10-1

Steps of construction :

  1. Plot the points (0, 1), (1, 0) and (2, -1) on graph paper.

  2. Connect points by straight line.

Solve the following simultaneous equations, graphically : 2x - 3y + 2 = 4x + 1 = 3x - y + 2. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

The two lines intersect at P(2, -1).

Hence, the solution of the given equations is x = 2, y = -1.

9Exercise 18.3

Use graph paper for this question :

(i) Draw the graphs of 3x - y - 2 = 0 and 2x + y - 8 = 0. Take 1 cm = 1 unit on both axes and plot three points per line.

(ii) Write down the coordinates of the point of intersection and the area of the triangle formed by the lines and the x-axis.

Show SolutionHide Solution↓

(i) Given,

⇒ 3x - y - 2 = 0

⇒ y = 3x - 2 ............(1)

When x = 0, y = 3 × 0 - 2 = 0 - 2 = -2,

x = 1, y = 3 × 1 - 2 = 3 - 2 = 1,

x = 2, y = 3 × 2 - 2 = 6 - 2 = 4.

Table of values for equation (1)

x012
y-214

Steps of construction :

  1. Plot the points (0, -2), (1, 1) and (2, 4).

  2. Join the points.

Given,

⇒ 2x + y - 8 = 0

⇒ y = 8 - 2x ...........(2)

When x = 2, y = 8 - 2 × 2 = 8 - 4 = 4,

x = 3, y = 8 - 2 × 3 = 8 - 6 = 2,

x = 4, y = 8 - 2 × 4 = 8 - 8 = 0.

Table of values for equation (2)

x234
y420

Steps of construction :

  1. Plot the points (2, 4), (3, 2) and (4, 0).

  2. Join the points.

Use graph paper for this question : (i) Draw the graphs of 3x - y - 2 = 0 and 2x + y - 8 = 0. Take 1 cm = 1 unit on both axes and plot three points per line. (ii) Write down the coordinates of the point of intersection and the area of the triangle formed by the lines and the x-axis. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

(ii) From the graph,

P(2, 4) is the point of intersection of lines.

BC = $3\frac{2}{3}$ cm

PV = 4 cm.

Area of triangle = $\frac{1}{2}$ × base × height

= $\frac{1}{2}$ × BC × PV

= $\frac{1}{2} \times 3\frac{2}{3}$ × 4

= $6\frac{2}{3}$ cm2.

Hence, P(2, 4) is the point of intersection of lines and area = $6\frac{2}{3}$ cm2.

10Exercise 18.3

Solve the following system of linear equations graphically :

2x - y - 4 = 0, x + y + 1 = 0.

Hence, find the area of the triangle formed by these lines and the y-axis.

Show SolutionHide Solution↓

Given,

⇒ 2x - y - 4 = 0

⇒ y = 2x - 4 ............(1)

When x = 1, y = 2(1) - 4 = 2 - 4 = -2,

x = 2, y = 2(2) - 4 = 4 - 4 = 0,

x = 3, y = 2(3) - 4 = 6 - 4 = 2.

Table of values for equation (1)

x123
y-202

Steps of construction :

  1. Plot the points (1, -2), (2, 0) and (3, 2).

  2. Join the points.

Given,

⇒ x + y + 1 = 0

⇒ y = -(x + 1) .............(2)

When, x = -1, y = -(-1 + 1) = 0,

x = 0, y = -(0 + 1) = -1,

x = 1, y = -(1 + 1) = -2.

Table of values for equation (2)

x-101
y0-1-2

Steps of construction :

  1. Plot the points (-1, 0), (0, -1) and (1, -2).

  2. Join the points.

Solve the following system of linear equations graphically : 2x - y - 4 = 0, x + y + 1 = 0. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

A(1, -2) is the point of intersection of lines.

ABC are the vertices of triangle.

From A, draw AD perpendicular to BC.

AD = 1 unit and BC = 3 units.

Area of △ABC = $\frac{1}{2}$ × base × height

= $\frac{1}{2}$ × BC × AD

= $\frac{1}{2}$ × 3 × 1

= $\frac{3}{2}$ sq. units

Hence, point of intersection = (1, -2) and area of triangle = $\frac{3}{2}$ sq. units

11Exercise 18.3

Solve graphically the following equations: x + 2y = 4, 3x - 2y = 4.

Take 2 cm = 1 unit on each axis. Write down the area of the triangle formed by the lines and the y-axis. Also, find the area of the triangle formed by the lines and the x-axis.

Show SolutionHide Solution↓

Given,

⇒ x + 2y = 4

⇒ 2y = 4 - x

⇒ y = $\frac{4 - x}{2}$ ......................(1)

When x = 0, y = $\frac{4 - 0}{2} = \frac{4}{2}$ = 2,

x = 2, y = $\frac{4 - 2}{2} = \frac{2}{2}$ = 1,

x = 4, y = $\frac{4 - 4}{2} = \frac{0}{2}$ = 0.

Table of values for equation (1)

x024
y210

Steps of construction :

  1. Plot the points (0, 2), (2, 1) and (4, 0).

  2. Join the points.

Given,

⇒ 3x - 2y = 4

⇒ 2y = 3x - 4

⇒ y = $\frac{3x - 4}{2}$ ..................(2)

When x = 0, y = $\frac{3 \times 0 - 4}{2} = \frac{0 - 4}{2} = \frac{-4}{2}$ = -2,

x = 2, y = $\frac{3 \times 2 - 4}{2} = \frac{6 - 4}{2} = \frac{2}{2}$ = 1,

x = 4, y = $\frac{3 \times 4 - 4}{2} = \frac{12 - 4}{2} = \frac{8}{2}$ = 4.

x = $\frac{4}{3}, y = \frac{3 \times \frac{4}{3} - 4}{2} = \frac{4 - 4}{2} = \frac{0}{2}$ = 0.

Table of values for equation (2)

x024$\frac{4}{3}$
y-2140

Steps of construction :

  1. Plot the points (0, -2), (2, 1), (4, 4) and $\Big(\frac{4}{3}, 0\Big)$.

  2. Join the points.

Solve graphically the following equations: x + 2y = 4, 3x - 2y = 4. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

A(2, 1) is the point of intersection of lines.

AEF is the triangle between lines and y-axis.

From A, draw AG perpendicular to EF.

Using distance formula, distance = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Distance between E (0, 2) and F (0, -2)

= $\sqrt{(0 - 0)^2 + \Big(2 - (-2)\Big)^2} = \sqrt{(2 + 2)^2} = \sqrt{4^2} = 4$ units

From graph,

AG = 2 units

EF = 4 units

Area of triangle = $\frac{1}{2}$ x base x height

= $\frac{1}{2}$ x EF x AG

= $\frac{1}{2}$ x 4 x 2

= 1 x 4

= 4 sq. units.

And, ABC is the triangle between lines and x-axis.

Using distance formula, distance = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Distance between B $\Big(\frac{4}{3}, 0\Big)$ and C (4, 0)

= $\sqrt{\Big(4 - \frac{4}{3}\Big)^2 + (0 - 0)^2} = \sqrt{\Big(\frac{12 - 4}{3}\Big)^2} = \sqrt{\Big(\frac{8}{3}\Big)^2} = \frac{8}{3}$

From A, draw AD perpendicular to BC.

AD = 1 unit

BC = $\frac{8}{3}$ units

Area of triangle = $\frac{1}{2}$ x base x height

$$\begin{aligned}\text{Area of triangle ABC} = \frac{1}{2} \times BC \times AD \\[1em] = \frac{1}{2} \times \frac{8}{3} \times 1 \\[1em] = \frac{4}{3} \text{sq. units}\end{aligned}$$

Hence, point of intersection of lines is x = 2, y = 1 and area of the triangle formed by the lines and the y-axis = 4 sq. unit and area of the triangle formed by the lines and the x-axis = $\frac{4}{3}$ sq units.

12Exercise 18.3

On graph paper, take 2 cm to represent one unit on both axes, draw the lines :

x + 3 = 0, y - 2 = 0, 2x + 3y = 12.

Write down the coordinates of the vertices of the triangle formed by these lines.

Show SolutionHide Solution↓

Given,

1st equation :

⇒ x + 3 = 0

⇒ x = -3 ............(1)

2nd equation :

⇒ y - 2 = 0

⇒ y = 2 .............(2)

3rd equation :

⇒ 2x + 3y = 12

⇒ 3y = 12 - 2x

⇒ y = $\frac{12 - 2x}{3}$ .........(3)

When, x = -3, y = $\frac{12 - 2 \times (-3)}{3} = \frac{12 + 6}{3} = \frac{18}{3}$ = 6,

x = 0, y = $\frac{12 - 2 \times 0}{3} = \frac{12}{3}$ = 4,

x = 3, y = $\frac{12 - 2 \times 3}{3} = \frac{12 - 6}{3} = \frac{6}{3}$ = 2.

Table of values of equation (3) :

x-303
y642

Steps of construction :

  1. Plot the points (-3, 6), (0, 4) and (3, 2).

  2. Join the points.

On graph paper, take 2 cm to represent one unit on both axes, draw the lines : x + 3 = 0, y - 2 = 0, 2x + 3y = 12. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

ABC is the required triangle.

Hence, coordinates of vertices of triangle formed by these lines = (-3, 6), (-3, 2) and (3, 2).

13Exercise 18.3

Find graphically the coordinates of the vertices of the triangle formed by the lines y = 0, y = x and 2x + 3y = 10. Hence, find the area of the triangle formed by these lines.

Show SolutionHide Solution↓

Given,

1st equation :

y = 0,

2nd equation :

y = x,

When, x = 0, y = 0,

x = 1, y = 1,

x = 2, y = 2.

Table of values of equation (2) :

x012
y012

Steps of construction :

  1. Plot the points (0, 0), (1, 1) and (2, 2).

  2. Join the points.

3rd equation :

⇒ 2x + 3y = 10

⇒ 3y = 10 - 2x

⇒ y = $\frac{10 - 2x}{3}$ ..........(3)

When, x = -1, y = $\frac{10 - 2 \times (-1)}{3} = \frac{10 + 2}{3} = \frac{12}{3}$ = 4,

x = 2, y = $\frac{10 - 2 \times 2}{3} = \frac{10 - 4}{3} = \frac{6}{3}$ = 2,

x = 5, y = $\frac{10 - 2 \times 5}{3} = \frac{10 - 10}{3}$ = 0.

Table of values of equation (3) :

x-125
y420

Steps of construction :

  1. Plot the points (-1, 4), (2, 2) and (5, 0).

  2. Join the points.

Find graphically the coordinates of the vertices of the triangle formed by the lines y = 0, y = x and 2x + 3y = 10. Hence, find the area of the triangle formed by these lines. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

ABC is the triangle.

From A, draw AD perpendicular to x-axis.

AD = 2 units and BC = 5 units.

Area of triangle = $\frac{1}{2}$ × base × height

= $\frac{1}{2} \times BC \times AD$

= $\frac{1}{2} \times 5 \times 2$

= 5 sq. units.

Hence, coordinates of triangle are (0, 0), (5, 0) and (2, 2) and area = 5 sq. units.

1(i)Exercise 18.4

Find the distance between the following pair of points :

(2, 3), (4, 1)

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Let P(x1, y1) and Q(x2, y2) be the given points

Co-ordinates of P = (2, 3)

Co-ordinates of Q = (4, 1)

$$\begin{aligned}PQ = \sqrt{(4 - 2)^2 + (1 - 3)^2} \\[1em] = \sqrt{2^2 + (-2)^2} \\[1em] = \sqrt{4 + 4}\\[1em] = \sqrt{8} \\[1em] = 2\sqrt{2}.\end{aligned}$$

Hence, distance between (2, 3) and (4, 1) = $2\sqrt{2}$ units.

1(ii)Exercise 18.4

Find the distance between the following pair of points :

(0, 0), (36, 15)

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Let P(x1, y1) and Q(x2, y2) be the given points

Co-ordinates of P = (0, 0)

Co-ordinates of Q = (36, 15)

$$\begin{aligned}PQ = \sqrt{(36 - 0)^2 + (15 - 0)^2} \\[1em] = \sqrt{36^2 + 15^2} \\[1em] = \sqrt{1296 + 225}\\[1em] = \sqrt{1521} \\[1em] = 39.\end{aligned}$$

Hence, distance between (0, 0) and (36, 15) = 39 units.

1(iii)Exercise 18.4

Find the distance between the following pair of points :

(a, b), (-a, -b)

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Let P(x1, y1) and Q(x2, y2) be the given points

Co-ordinates of P = (a, b)

Co-ordinates of Q = (-a, -b)

$$\begin{aligned}PQ = \sqrt{(-a - a)^2 + (-b - b)^2} \\[1em] = \sqrt{(-2a)^2 + (-2b)^2} \\[1em] = \sqrt{4a^2 + 4b^2}\\[1em] = \sqrt{4(a^2 + b^2)} \\[1em] = 2\sqrt{a^2 + b^2}.\end{aligned}$$

Hence, distance between (a, b) and (-a, -b) = $2\sqrt{a^2 + b^2}$ units.

2Exercise 18.4

A is a point on y-axis whose ordinate is 4 and B is a point on x-axis whose abscissa is -3. Find the length of the line segment AB.

Show SolutionHide Solution↓

Since, point A is on y-axis so its x-coordinate = 0.

Given,

Ordinate of A = 4.

∴ A = (0, 4).

Since, point B is on x-axis so its y-coordinate = 0.

Given,

Abscissa of B = -3.

∴ B = (-3, 0).

By distance formula,

$$\begin{aligned}\Rightarrow d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(-3 - 0)^2 + (0 - 4)^2} \\[1em] = \sqrt{(-3)^2 + (-4)^2} \\[1em] = \sqrt{9 + 16} \\[1em] = \sqrt{25} \\[1em] = 5.\end{aligned}$$

Hence, AB = 5 units.

3Exercise 18.4

Find the value of a, if the distance between the points A (-3, -14) and B (a, -5) is 9 units.

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}\Rightarrow AB = \sqrt{[a - (-3)]^2 + [(-5) - (-14)]^2} \\[1em] \Rightarrow 9 = \sqrt{(a + 3)^2 + (-5 + 14)^2} \\[1em] \Rightarrow 9 = \sqrt{a^2 + 9 + 6a + (9)^2} \\[1em] \Rightarrow 9 = \sqrt{a^2 + 6a + 9 + 81}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow a^2 + 6a + 90 = (9)^2 \\[1em] \Rightarrow a^2 + 6a + 90 = 81 \\[1em] \Rightarrow a^2 + 6a + 90 - 81 = 0 \\[1em] \Rightarrow a^2 + 6a + 9 = 0 \\[1em] \Rightarrow a^2 + 3a + 3a + 9 = 0 \\[1em] \Rightarrow a(a + 3) + 3(a + 3) = 0 \\[1em] \Rightarrow (a + 3)(a + 3) = 0 \\[1em] \Rightarrow a + 3 = 0 \\[1em] \Rightarrow a = -3.\end{aligned}$$

Hence, value of a = -3.

4(i)Exercise 18.4

Find points on the x-axis which are at a distance of 5 units from the point (5, -4).

Show SolutionHide Solution↓

We know that,

y-coordinate of any point on x-axis = 0.

Let point on x-axis which is at a distance of 5 units from (5, -4) be P(x, 0).

By distance formula,

$$\begin{aligned}\Rightarrow d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \Rightarrow 5 = \sqrt{(x - 5)^2 + [0 - (-4)]^2} \\[1em] \Rightarrow 5 = \sqrt{x^2 + 25 - 10x + 16} \\[1em] \Rightarrow (5)^2 = x^2 - 10x + 41\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow 25 = x^2 - 10x + 41 \\[1em] \Rightarrow x^2 - 10x + 41 - 25 = 0 \\[1em] \Rightarrow x^2 - 10x + 16 = 0 \\[1em] \Rightarrow x^2 - 8x - 2x + 16 = 0 \\[1em] \Rightarrow x(x - 8) - 2(x - 8) = 0 \\[1em] \Rightarrow (x - 2)(x - 8) = 0 \\[1em] \Rightarrow x - 2 = 0 \text{ or } x - 8 = 0 \\[1em] \Rightarrow x = 2 \text{ or } x = 8.\end{aligned}$$

∴ P = (x, 0) = (2, 0) or (8, 0).

Hence, points on the x-axis which are at a distance of 5 units from the point (5, -4) are (2, 0) or (8, 0).

4(ii)Exercise 18.4

Find points on the y-axis which are at a distance of 10 units from the point (8, 8).

Show SolutionHide Solution↓

We know that,

x-coordinate of any point on y-axis = 0.

Let point on y-axis which is at a distance of 10 units from (8, 8) be P(0, y).

By distance formula,

$$\begin{aligned}\Rightarrow d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \Rightarrow 10 = \sqrt{(0 - 8)^2 + (y - 8)^2} \\[1em] \Rightarrow 10 = \sqrt{(-8)^2 + y^2 + 8^2 - 16y} \\[1em] \Rightarrow 10 = \sqrt{64 + y^2 + 64 - 16y} \\[1em]\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow 10^2 = 64 + y^2 + 64 - 16y \\[1em] \Rightarrow 100 = y^2 + 128 - 16y \\[1em] \Rightarrow y^2 - 16y + 128 - 100 = 0 \\[1em] \Rightarrow y^2 - 16y + 28 = 0 \\[1em] \Rightarrow y^2 - 14y - 2y + 28 = 0 \\[1em] \Rightarrow y(y - 14) - 2(y - 14) = 0 \\[1em] \Rightarrow (y - 2)(y - 14) = 0 \\[1em] \Rightarrow y - 2 = 0 \text{ or } y - 14 = 0 \\[1em] \Rightarrow y = 2 \text{ or } y = 14.\end{aligned}$$

∴ P = (0, y) = (0, 2) or (0, 14).

Hence, points on the y-axis which are at a distance of 10 units from the point (8, 8) are (0, 2) or (0, 14).

4(iii)Exercise 18.4

Find point (or points) which are at distance of $\sqrt{10}$ units from the point (4, 3) given that the ordinate of the point (or points) is twice the abscissa.

Show SolutionHide Solution↓

Given,

Ordinate of the point is twice the abscissa.

Let abscissa of point be k, then ordinate = 2k

Let the required point be P.

∴ P = (k, 2k).

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Given,

Distance between (4, 3) and (k, 2k) = $\sqrt{10}$ units.

$$\begin{aligned}\Rightarrow \sqrt{10} = \sqrt{(k - 4)^2 + (2k - 3)^2} \\[1em] \Rightarrow \sqrt{10} = \sqrt{k^2 + (4)^2 - 8k + (2k)^2 + (3)^2 - 12k} \\[1em] \Rightarrow \sqrt{10} = \sqrt{k^2 + 16 - 8k + 4k^2 + 9 - 12k}\end{aligned}$$

On squaring both sides

$$\begin{aligned}\Rightarrow 10 = k^2 + 16 - 8k + 4k^2 + 9 - 12k \Rightarrow 10 = 5k^2 - 20k + 25 \\[1em] \Rightarrow 10 = 5(k^2 - 4k + 5) \\[1em] \Rightarrow k^2 - 4k + 5 = 2 \\[1em] \Rightarrow k^2 - 4k + 5 - 2 = 0 \\[1em] \Rightarrow k^2 - 4k + 3 = 0 \\[1em] \Rightarrow k^2 - 3k - k + 3 = 0 \\[1em] \Rightarrow k(k - 3) - 1(k - 3) = 0 \\[1em] \Rightarrow (k - 1)(k - 3) = 0 \\[1em] \Rightarrow k - 1 = 0 \text{ or } k - 3 = 0 \\[1em] \Rightarrow k = 1 \text{ or } k = 3.\end{aligned}$$

When k = 1,

P = (k, 2k) = (1, 2).

When k = 3,

P = (k, 2k) = (3, 6).

Hence, required points are (1, 2) or (3, 6).

5Exercise 18.4

Find the point on the x-axis which is equidistant from the points (2, -5) and (-2, 9).

Show SolutionHide Solution↓

We know that,

y-coordinate of any point on x-axis = 0.

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Let point on x-axis which is equidistant from the points (2, -5) and (-2, 9) be P(x, 0).

∴ Distance between (2, -5) and (x, 0) = Distance between (-2, 9) and (x, 0).

$$\begin{aligned}\Rightarrow \sqrt{(x - 2)^2 + [0 - (-5)]^2} = \sqrt{[x - (-2)]^2 + (0 - 9)^2} \\[1em] \Rightarrow \sqrt{x^2 + 4 - 4x + 5^2} = \sqrt{(x + 2)^2 + (-9)^2} \\[1em] \Rightarrow \sqrt{x^2 - 4x + 25 + 4} = \sqrt{x^2 + 4 + 4x + 81} \\[1em]\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow x^2 - 4x + 29 = x^2 + 4x + 85 \\[1em] \Rightarrow x^2 - x^2 + 4x + 4x = 29 - 85 \\[1em] \Rightarrow 8x = -56 \\[1em] \Rightarrow x = -7.\end{aligned}$$

P = (x, 0) = (-7, 0).

Hence, required point is (-7, 0).

6Exercise 18.4

Find the value of x such that PQ = QR where the coordinates of P, Q and R are (6, -1), (1, 3) and (x, 8) respectively.

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Given, PQ = QR.

∴ Distance between (6, -1) and (1, 3) = Distance between (1, 3) and (x, 8).

$$\begin{aligned}\Rightarrow \sqrt{(1 - 6)^2 + [3 - (-1)]^2} = \sqrt{(x - 1)^2 + (8 - 3)^2} \\[1em] \Rightarrow \sqrt{(-5)^2 + [4]^2} = \sqrt{x^2 + 1 - 2x + (5)^2} \\[1em] \Rightarrow \sqrt{25 + 16} = \sqrt{x^2 - 2x + 1 + 25} \\[1em] \Rightarrow \sqrt{41} = \sqrt{x^2 - 2x + 26}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow 41 = x^2 - 2x + 26 \\[1em] \Rightarrow x^2 - 2x + 26 - 41 = 0 \\[1em] \Rightarrow x^2 - 2x - 15 = 0 \\[1em] \Rightarrow x^2 - 5x + 3x - 15 = 0 \\[1em] \Rightarrow x(x - 5) + 3(x - 5) = 0 \\[1em] \Rightarrow (x + 3)(x - 5) = 0 \\[1em] \Rightarrow x = -3 \text{ or } x = 5.\end{aligned}$$

Hence, x = -3 or 5.

7Exercise 18.4

If Q(0, 1) is equidistant from P(5, -3) and R(x, 6), find the values of x.

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Given,

∴ Distance between Q(0, 1) and P(5, -3) = Distance between Q(0, 1) and R(x, 6).

$$\begin{aligned}\Rightarrow \sqrt{(5 - 0)^2 + (-3 - 1)^2} = \sqrt{(x - 0)^2 + (6 - 1)^2} \\[1em] \Rightarrow \sqrt{5^2 + (-4)^2} = \sqrt{x^2 + 5^2} \\[1em] \Rightarrow \sqrt{25 + 16} = \sqrt{x^2 + 25}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow 25 + 16 = x^2 + 25 \\[1em] \Rightarrow x^2 = 16 \\[1em] \Rightarrow x = \sqrt{16} \\[1em] \Rightarrow x = \pm 4.\end{aligned}$$

Hence, x = ±4.

8Exercise 18.4

Find a relation between x and y such that point (x, y) is equidistant from the points (7, 1) and (3, 5).

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Given,

∴ Distance between (x, y) and (7, 1) = Distance between (x, y) and (3, 5).

$$\begin{aligned}\therefore \sqrt{(7 - x)^2 + (1 - y)^2} = \sqrt{(3 - x)^2 + (5 - y)^2} \\[1em] \Rightarrow \sqrt{49 + x^2 - 14x + 1 + y^2 - 2y} = \sqrt{9 + x^2 - 6x + 25 + y^2 - 10y}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow 49 + x^2 - 14x + 1 + y^2 - 2y = 9 + x^2 - 6x + 25 + y^2 - 10y \\[1em] \Rightarrow x^2 + y^2 - 14x - 2y + 50 = x^2 + y^2 - 6x - 10y + 34 \\[1em] \Rightarrow x^2 + y^2 - x^2 - y^2 - 6x + 14x = 10y - 2y + 50 - 34 \\[1em] \Rightarrow 8x = 8y + 16 \\[1em] \Rightarrow 8x = 8(y + 2) \\[1em] \Rightarrow x = y + 2 \\[1em] \Rightarrow x - y = 2.\end{aligned}$$

Hence, relation between x and y is x - y = 2.

9Exercise 18.4

The x-coordinate of a point P is twice its y-coordinate. If P is equidistant from the points Q(2, -5) and R(-3, 6), then find the coordinates of P.

Show SolutionHide Solution↓

Let y-coordinate of point P be k.

∴ x-coordinate = 2k.

P = (2k, k)

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Given,

P is equidistant from the points Q(2, -5) and R(-3, 6).

$$\begin{aligned}\Rightarrow \sqrt{(2 - 2k)^2 + (-5 - k)^2} = \sqrt{(-3 - 2k)^2 + (6 - k)^2} \\[1em] \Rightarrow \sqrt{4 + 4k^2 - 8k + 25 + k^2 + 10k} = \sqrt{9 + 4k^2 + 12k + 36 + k^2 - 12k} \\[1em] \Rightarrow \sqrt{5k^2 + 2k + 29} = \sqrt{5k^2 + 45}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow 5k^2 + 2k + 29 = 5k^2 + 45 \\[1em] \Rightarrow 5k^2 - 5k^2 + 2k = 45 - 29 \\[1em] \Rightarrow 2k = 16 \\[1em] \Rightarrow k = \frac{16}{2} \\[1em] \Rightarrow k = 8.\end{aligned}$$

P = (2k, k) = (16, 8).

Hence, coordinates of P = (16, 8).

10Exercise 18.4

If the points A(4, 3) and B(x, 5) are on a circle with center C(2, 3), find the values of x.

Show SolutionHide Solution↓

Given,

A(4, 3) and B(x, 5) are on a circle with center C(2, 3).

If the points A(4, 3) and B(x, 5) are on a circle with center C(2, 3), find the values of x. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

∴ AC = BC [Radius of same circle]

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Substituting values in above equation, we get :

$$\begin{aligned}\Rightarrow \sqrt{(2 - 4)^2 + (3 - 3)^2} = \sqrt{(2 - x)^2 + (3 - 5)^2} \\[1em] \Rightarrow \sqrt{(-2)^2} = \sqrt{4 + x^2 - 4x + (-2)^2} \\[1em] \Rightarrow \sqrt{4} = \sqrt{4 + x^2 - 4x + 4}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow 4 = x^2 - 4x + 8 \\[1em] \Rightarrow x^2 - 4x + 4 = 0 \\[1em] \Rightarrow x^2 - 2x - 2x + 4 = 0 \\[1em] \Rightarrow x(x - 2) - 2(x - 2) = 0 \\[1em] \Rightarrow (x - 2)(x - 2) = 0 \\[1em] \Rightarrow x - 2 = 0 \\[1em] \Rightarrow x = 2.\end{aligned}$$

Hence, value of x = 2.

11Exercise 18.4

If a point A(0, 2) is equidistant from the points B(3, p) and C(p, 5), then find the value of p.

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Given,

AB = AC.

$$\begin{aligned}\Rightarrow \sqrt{(3 - 0)^2 + (p - 2)^2} = \sqrt{(p - 0)^2 + (5 - 2)^2} \\[1em] \Rightarrow \sqrt{3^2 + p^2 + 4 - 4p} = \sqrt{p^2 + 3^2} \\[1em] \Rightarrow \sqrt{9 + p^2 + 4 - 4p} = \sqrt{p^2 + 3^2}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow p^2 + 13 - 4p = p^2 + 9 \\[1em] \Rightarrow p^2 - p^2 + 4p = 13 - 9 \\[1em] \Rightarrow 4p = 4 \\[1em] \Rightarrow p = 1.\end{aligned}$$

Hence, p = 1.

12Exercise 18.4

Using distance formula, show that (3, 3) is the center of the circle passing through the points (6, 2), (0, 4) and (4, 6).

Show SolutionHide Solution↓

Given,

Center (O) = (3, 3)

Let, A = (6, 2), B = (0, 4) and C = (4, 6).

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \Rightarrow AO = \sqrt{(6 - 3)^2 + (2 - 3)^2} \\[1em] = \sqrt{(3)^2 + (-1)^2} \\[1em] = \sqrt{9 + 1} \\[1em] = \sqrt{10}. \\[1em] \Rightarrow BO = \sqrt{(0 - 3)^2 + (4 - 3)^2} \\[1em] = \sqrt{(-3)^2 + 1^2} \\[1em] = \sqrt{9 + 1} \\[1em] = \sqrt{10}. \\[1em] \Rightarrow CO = \sqrt{(4 - 3)^2 + (6 - 3)^2} \\[1em] = \sqrt{1^2 + 3^2} \\[1em] = \sqrt{1 + 9} \\[1em] = \sqrt{10}. \\[1em]\end{aligned}$$

Since, AO = BO = CO.

Hence, proved that (3, 3) is the center of the circle passing through the points (6, 2), (0, 4) and (4, 6).

13Exercise 18.4

The center of a circle is C(2α - 1, 3α + 1) and it passes through the point A(-3, -1). If a diameter of the circle is of length 20 units, find the value(s) of α.

Show SolutionHide Solution↓

Given,

Diameter = 20 units

Radius = $\frac{\text{Diameter}}{2} = \frac{20}{2}$ = 10 units.

∴ AC = 10 units

The center of a circle is C(2α - 1, 3α + 1) and it passes through the point A(-3, -1). If a diameter of the circle is of length 20 units, find the value(s) of α. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

$$\begin{aligned}\Rightarrow \sqrt{[-3 - (2α - 1)]^2 + [-1 - (3α + 1)]^2} = 10 \\[1em] \Rightarrow \sqrt{(-3 - 2α + 1)^2 + (-1 - 3α - 1)^2} = 10 \\[1em] \Rightarrow \sqrt{(-2 - 2α)^2 + (-3α - 2)^2} = 10 \\[1em] \Rightarrow \sqrt{4 + 4α^2 + 8α + 9α^2 + 4 + 12α} = 10 \\[1em] \Rightarrow \sqrt{13α^2 + 20α + 8} = 10\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow 13α^2 + 20α + 8 = 10^2 \\[1em] \Rightarrow 13α^2 + 20α + 8 = 100 \\[1em] \Rightarrow 13α^2 + 20α + 8 - 100 = 0 \\[1em] \Rightarrow 13α^2 + 20α - 92 = 0 \\[1em] \Rightarrow 13α^2 + 46α - 26α - 92 =0 \\[1em] \Rightarrow α(13α + 46) - 2(13α + 46) = 0 \\[1em] \Rightarrow (13α + 46)(α - 2) = 0 \\[1em] \Rightarrow 13α + 46 = 0 \text{ or } α - 2 = 0 \\[1em] \Rightarrow 13α = -46 \text{ or } α = 2 \\[1em] \Rightarrow α = -\frac{46}{13} \text{ or } α = 2.\end{aligned}$$

Hence, α = $-\frac{46}{13}$ or α = 2.

14Exercise 18.4

Using distance formula, show that the points A(3, 1), B(6, 4) and C(8, 6) are collinear.

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}AB = \sqrt{(6 - 3)^2 + (4 - 1)^2} \\[1em] = \sqrt{3^2 + 3^2} \\[1em] = \sqrt{9 + 9} \\[1em] = \sqrt{18} \\[1em] = 3\sqrt{2}. \\[1em] BC = \sqrt{(8 - 6)^2 + (6 - 4)^2} \\[1em] = \sqrt{2^2 + 2^2} \\[1em] = \sqrt{4 + 4} \\[1em] = \sqrt{8} \\[1em] = 2\sqrt{2}. \\[1em] AC = \sqrt{(8 - 3)^2 + (6 - 1)^2} \\[1em] = \sqrt{5^2 + 5^2} \\[1em] = \sqrt{25 + 25} \\[1em] = \sqrt{50} \\[1em] = 5\sqrt{2}. \\[1em] \Rightarrow AB + BC = 3\sqrt{2} + 2\sqrt{2} = 5\sqrt{2} = AC.\end{aligned}$$

Thus, AC = AB + BC.

Hence, proved that A, B and C are collinear.

15Exercise 18.4

Check whether the points (5, -2), (6, 4) and (7, -2) are the vertices of an isosceles triangle.

Show SolutionHide Solution↓

Let points be A(5, -2), B(6, 4) and C(7, -2).

Check whether the points (5, -2), (6, 4) and (7, -2) are the vertices of an isosceles triangle. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}AB = \sqrt{(6 - 5)^2 + [4 - (-2)]^2} \\[1em] = \sqrt{1^2 + 6^2} \\[1em] = \sqrt{1 + 36} \\[1em] = \sqrt{37}. \\[1em] BC = \sqrt{(7 - 6)^2 + [-2 - 4]^2} \\[1em] = \sqrt{1^2 + (-6)^2} \\[1em] = \sqrt{37}.\end{aligned}$$

Since, AB = BC.

Hence, proved that (5, -2), (6, 4) and (7, -2) are the vertices of an isosceles triangle.

16Exercise 18.4

Name the type of triangle formed by the points A(-5, 6), B(-4, -2) and C(7, 5).

Show SolutionHide Solution↓

By distance formula,

Name the type of triangle formed by the points A(-5, 6), B(-4, -2) and C(7, 5). Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}AB = \sqrt{[-4 - (-5)]^2 + [-2 - 6]^2} \\[1em] = \sqrt{(-4 + 5)^2 + (-8)^2} \\[1em] = \sqrt{1^2 + 64} \\[1em] = \sqrt{65}. \\[1em] BC = \sqrt{[7 - (-4)]^2 + [5 - (-2)]^2} \\[1em] = \sqrt{11^2 + 7^2} \\[1em] = \sqrt{121 + 49} \\[1em] = \sqrt{170}. \\[1em] AC = \sqrt{[7 - (-5)]^2 + (5 - 6)^2} \\[1em] = \sqrt{12^2 + (-1)^2} \\[1em] = \sqrt{144 + 1} \\[1em] = \sqrt{145}.\end{aligned}$$

Since, AB ≠ BC ≠ AC.

Hence, ABC is a scalene triangle.

17Exercise 18.4

Show that the points A(1, 1), B(-1, -1) and C(-$\sqrt{3}, \sqrt{3}$) form an equilateral triangle.

Show SolutionHide Solution↓

By distance formula,

Show that the points A(1, 1), B(-1, -1) and C form an equilateral triangle. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}AB = \sqrt{(-1 - 1)^2 + (-1 - 1)^2} \\[1em] = \sqrt{(-2)^2 + (-2)^2} \\[1em] = \sqrt{4 + 4} \\[1em] = \sqrt{8} \\[1em] = 2\sqrt{2}. \\[1em] BC = \sqrt{[-\sqrt{3} - (-1)]^2 + [\sqrt{3} - (-1)]^2} \\[1em] = \sqrt{[-\sqrt{3} + 1]^2 + [\sqrt{3} + 1]^2} \\[1em] = \sqrt{3 + 1 - 2\sqrt{3} + 3 + 1 + 2\sqrt{3}} \\[1em] = \sqrt{8} \\[1em] = 2\sqrt{2}. \\[1em] AC = \sqrt{[-\sqrt{3} - 1]^2 + [\sqrt{3} - 1]^2} \\[1em] = \sqrt{3 + 1 + 2\sqrt{3} + 3 + 1 - 2\sqrt{3}} \\[1em] = \sqrt{8} \\[1em] = 2\sqrt{2}. \\[1em]\end{aligned}$$

Since, AB = BC = AC.

Hence, ABC is an equilateral triangle.

18Exercise 18.4

Show that the points (7, 10), (-2, 5) and (3, -4) are the vertices of an isosceles right triangle.

Show SolutionHide Solution↓

Let points be A(7, 10), B(-2, 5) and C(3, -4).

Show that the points (7, 10), (-2, 5) and (3, -4) are the vertices of an isosceles right triangle. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}AB = \sqrt{(-2 - 7)^2 + (5 - 10)^2} \\[1em] = \sqrt{(-9)^2 + (-5)^2} \\[1em] = \sqrt{81 + 25} \\[1em] = \sqrt{106} \text{ units}. \\[1em] BC = \sqrt{[3 - (-2)]^2 + [-4 - 5]^2} \\[1em] = \sqrt{5^2 + (-9)^2} \\[1em] = \sqrt{25 + 81} \\[1em] = \sqrt{106} \text{ units}. \\[1em] AC = \sqrt{(3 - 7)^2 + (-4 - 10)^2} \\[1em] = \sqrt{(-4)^2 + (-14)^2} \\[1em] = \sqrt{16 + 196} \\[1em] = \sqrt{212} \text{ units}.\end{aligned}$$

⇒ AB2 + BC2 = $(\sqrt{106})^2 + (\sqrt{106})^2$

= 106 + 106

= 212

= AC2.

Since, AB = BC and AB2 + BC2 = AC2.

∴ ABC is an isosceles right angle triangle, right angled at B.

Hence, proved that (7, 10), (-2, 5) and (3, -4) are the vertices of an isosceles triangle.

19Exercise 18.4

The points A(0, 3), B(-2, a) and C(-1, 4) are the vertices of a right angled triangle at A, find the value of a.

Show SolutionHide Solution↓

By distance formula,

The points A(0, 3), B(-2, a) and C(-1, 4) are the vertices of a right angled triangle at A, find the value of a. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}AB = \sqrt{(-2 - 0)^2 + (a - 3)^2} \\[1em] = \sqrt{(-2)^2 + a^2 + 9 - 6a} \\[1em] = \sqrt{4 + a^2 + 9 - 6a} \\[1em] = \sqrt{a^2 - 6a + 13}. \\[1em] BC = \sqrt{[-1 - (-2)]^2 + (4 - a)^2} \\[1em] = \sqrt{(-1 + 2)^2 + (4 - a)^2} \\[1em] = \sqrt{(1)^2 + 16 + a^2 - 8a} \\[1em] = \sqrt{1 + 16 + a^2 - 8a} \\[1em] = \sqrt{a^2 - 8a + 17}. \\[1em] AC = \sqrt{(-1 - 0)^2 + (4 - 3)^2} \\[1em] = \sqrt{(-1)^2 + (1)^2} \\[1em] = \sqrt{1 + 1} \\[1em] = \sqrt{2}.\end{aligned}$$

By pythagoras theorem,

AB2 + AC2 = BC2

$$\begin{aligned}\Rightarrow \Big(\sqrt{a^2 - 6a + 13}\Big)^2 + \Big(\sqrt{2}\Big)^2 = \Big(\sqrt{a^2 - 8a + 17}\Big)^2 \\[1em] \Rightarrow a^2 - 6a + 13 + 2 = a^2 - 8a + 17 \\[1em] \Rightarrow a^2 - a^2 - 6a + 8a = 17 - 15 \\[1em] \Rightarrow 2a = 2 \\[1em] \Rightarrow a = 1.\end{aligned}$$

Hence, value of a = 1.

20Exercise 18.4

Show that the points (0, -1), (-2, 3), (6, 7) and (8, 3), taken in order, are the vertices of a rectangle. Also find its area.

Show SolutionHide Solution↓

Let A(0, -1), B(-2, 3), C(6, 7) and D(8, 3).

Show that the points (0, -1), (-2, 3), (6, 7) and (8, 3), taken in order, are the vertices of a rectangle. Also find its area. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}AB = \sqrt{(-2 - 0)^2 + [3 - (-1)]^2} \\[1em] = \sqrt{(-2)^2 + [3 + 1]^2}\\[1em] = \sqrt{4 + 4^2} \\[1em] = \sqrt{4 + 16} \\[1em] = \sqrt{20}. \\[1em] BC = \sqrt{[6 - (-2)]^2 + (7 - 3)^2} \\[1em] = \sqrt{[6 + 2]^2 + (4)^2} \\[1em] = \sqrt{8^2 + 4^2} \\[1em] = \sqrt{64 + 16} \\[1em] = \sqrt{80}. \\[1em] CD = \sqrt{(8 - 6)^2 + (3 - 7)^2} \\[1em] = \sqrt{2^2 + (-4)^2} \\[1em] = \sqrt{4 + 16} \\[1em] = \sqrt{20} \\[1em] AD = \sqrt{(8 - 0)^2 + [3 - (-1)]^2} \\[1em] = \sqrt{8^2 + [3 + 1]^2} \\[1em] = \sqrt{64 + 4^2} \\[1em] = \sqrt{64 + 16} \\[1em] = \sqrt{80}.\end{aligned}$$

Since, AB = CD and BC = AD.

∴ ABCD is a rectangle.

Area of rectangle ABCD = AB × BC

$$\begin{aligned}= \sqrt{20} \times \sqrt{80} \\[1em] = 2\sqrt{5} \times 4\sqrt{5} \\[1em] = 8 \times 5 \\[1em] = 40 \text{ sq. units}.\end{aligned}$$

Hence, area of rectangle = 40 sq. units.

21Exercise 18.4

If P(2, -1), Q(3, 4), R(-2, 3) and S(-3, -2) be four points in a plane, show that PQRS is a rhombus but not a square. Find the area of the rhombus.

Show SolutionHide Solution↓

By distance formula,

If P(2, -1), Q(3, 4), R(-2, 3) and S(-3, -2) be four points in a plane, show that PQRS is a rhombus but not a square. Find the area of the rhombus. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}PQ = \sqrt{(3 - 2)^2 + [4 - (-1)]^2} \\[1em] = \sqrt{1^2 + [4 + 1]^2} \\[1em] = \sqrt{1 + 5^2} \\[1em] = \sqrt{1 + 25} \\[1em] = \sqrt{26}. \\[1em] QR = \sqrt{(-2 - 3)^2 + (3 - 4)^2} \\[1em] = \sqrt{(-5)^2 + (-1)^2} \\[1em] = \sqrt{25 + 1} \\[1em] = \sqrt{26}. \\[1em] RS = \sqrt{[-3 - (-2)]^2 + [-2 - 3]^2} \\[1em] = \sqrt{[-3 + 2]^2 + [-5]^2} \\[1em] = \sqrt{[-1]^2 + 25} \\[1em] = \sqrt{26}. \\[1em] PS = \sqrt{[-3 - 2]^2 + [-2 - (-1)]^2} \\[1em] = \sqrt{[-5]^2 + [-2 + 1]^2} \\[1em] = \sqrt{25 + [-1]^2} \\[1em] = \sqrt{25 + 1} \\[1em] = \sqrt{26}.\end{aligned}$$

Here, PQ = QR = RS = PS.

So, PQRS can be a square or rhombus.

Calculating diagonal,

$$\begin{aligned}PR = \sqrt{(-2 - 2)^2 + [3 - (-1)]^2} \\[1em] = \sqrt{(-4)^2 + [3 + 1]^2} \\[1em] = \sqrt{16 + 4^2} \\[1em] = \sqrt{16 + 16} \\[1em] = \sqrt{32} \\[1em] = 4\sqrt{2}. \\[1em] QS = \sqrt{(-3 - 3)^2 + (-2 - 4)^2} \\[1em] = \sqrt{(-6)^2 + (-6)^2} \\[1em] = \sqrt{36 + 36} \\[1em] = \sqrt{72} \\[1em] = 6\sqrt{2}.\end{aligned}$$

PR ≠ QS.

Since, diagonal of rhombus are not equal,

∴ PQRS is a rhombus

Area of rhombus = $\frac{1}{2} \times d_1 \times d_2$

= $\frac{1}{2} \times 4\sqrt{2} \times 6\sqrt{2}$

= $\frac{48}{2}$ = 24 sq. units.

Hence, PQRS is a rhombus and area = 24 sq. units.

22Exercise 18.4

Prove that the points A(2, 3), B(-2, 2), C(-1, -2) and D(3, -1) are the vertices of a square ABCD.

Show SolutionHide Solution↓

By distance formula,

Prove that the points A(2, 3), B(-2, 2), C(-1, -2) and D(3, -1) are the vertices of a square ABCD. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}AB = \sqrt{(-2 - 2)^2 + (2 - 3)^2} \\[1em] = \sqrt{(-4)^2 + (-1)^2} \\[1em] = \sqrt{16 + 1} \\[1em] = \sqrt{17}. \\[1em] BC = \sqrt{[-1 - (-2)]^2 + [-2 - 2]^2} \\[1em] = \sqrt{[-1 + 2]^2 + [-4]^2} \\[1em] = \sqrt{1^2 + 16} \\[1em] = \sqrt{17}. \\[1em] CD = \sqrt{[3 - (-1)]^2 + [-1 - (-2)]^2} \\[1em] = \sqrt{[3 + 1]^2 + [-1 + 2]^2} \\[1em] = \sqrt{4^2 + 1^2} \\[1em] = \sqrt{16 + 1} \\[1em] = \sqrt{17}. \\[1em] AD = \sqrt{(3 - 2)^2 + (-1 - 3)^2} \\[1em] = \sqrt{1^2 + (-4)^2} \\[1em] = \sqrt{1 + 16} \\[1em] = \sqrt{17}.\end{aligned}$$

Calculating diagonals,

$$\begin{aligned}AC = \sqrt{(-1 - 2)^2 + (-2 - 3)^2} \\[1em] = \sqrt{(-3)^2 + (-5)^2} \\[1em] = \sqrt{9 + 25} \\[1em] = \sqrt{34}. \\[1em] BD = \sqrt{[3 - (-2)]^2 + (-1 - 2)^2} \\[1em] = \sqrt{[3 + 2]^2 + (-3)^2} \\[1em] = \sqrt{5^2 + 9} \\[1em] = \sqrt{25 + 9} \\[1em] = \sqrt{34}.\end{aligned}$$

Since, AB = BC =CD = AD and AC = BD.

Hence, proved that A, B, C and D are the vertices of a square.

23(i)Exercise 18.4

Name the type of quadrilateral formed by the following points and give reasons for your answer :

(-1, -2), (1, 0), (-1, 2), (-3, 0).

Show SolutionHide Solution↓

Let coordinates be A(-1, -2), B(1, 0), C(-1, 2) and D(-3, 0).

$$\begin{aligned}AB = \sqrt{[1 - (-1)]^2 + [0 - (-2)]^2} \\[1em] = \sqrt{[1 + 1]^2 + [0 + 2]^2}\\[1em] = \sqrt{2^2 + 2^2} \\[1em] = \sqrt{4 + 4} \\[1em] = \sqrt{8}. \\[1em] BC = \sqrt{(-1 - 1)^2 + (2 - 0)^2} \\[1em] = \sqrt{(-2)^2 + (2)^2} \\[1em] = \sqrt{4 + 4} \\[1em] = \sqrt{8}. \\[1em] CD = \sqrt{[-3 - (-1)]^2 + [0 - 2]^2} \\[1em] = \sqrt{[-3 + 1]^2 + [-2]^2} \\[1em] = \sqrt{[-2]^2 + [-2]^2} \\[1em] = \sqrt{4 + 4} \\[1em] = \sqrt{8}. \\[1em] AD = \sqrt{[-3 - (-1)]^2 + [0 - (-2)]^2} \\[1em] = \sqrt{[-3 + 1]^2 + [2]^2} \\[1em] =\sqrt{[-2]^2 + [2]^2} \\[1em] = \sqrt{4 + 4} \\[1em] = \sqrt{8}.\end{aligned}$$

Since, AB = BC = CD = AD.

So, ABCD can be square or rhombus.

Calculating diagonal,

$$\begin{aligned}AC = \sqrt{[-1 - (-1)]^2 + [2 - (-2)]^2} \\[1em] = \sqrt{[-1 + 1]^2 + [2 + 2]^2} \\[1em] = \sqrt{0 + 4^2} \\[1em] = \sqrt{16} \\[1em] = 4. \\[1em] BD = \sqrt{(-3 - 1)^2 + (0 - 0)^2} \\[1em] = \sqrt{(-4)^2 + 0^2} \\[1em] = \sqrt{16} \\[1em] = 4.\end{aligned}$$

Since, diagonals are also equal.

Hence, (-1, -2), (1, 0), (-1, 2), (-3, 0) are the vertices of a square.

23(ii)Exercise 18.4

Name the type of quadrilateral formed by the following points and give reasons for your answer :

(4, 5), (7, 6), (4, 3), (1, 2)

Show SolutionHide Solution↓

Let A(4, 5), B(7, 6), C(4, 3), D(1, 2) are the given points.

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(7 - 4)^2 + (6 - 5)^2} \\[1em] = \sqrt{3^2 + 1^2} \\[1em] = \sqrt{9 + 1} \\[1em] = \sqrt{10} \text{ units}. \\[1em] BC = \sqrt{(4 - 7)^2 + (3 - 6)^2} \\[1em] = \sqrt{(-3)^2 + (-3)^2} \\[1em] = \sqrt{9 + 9} \\[1em] = \sqrt{18} \\[1em] = 3\sqrt{2} \text{ units}. \\[1em] CD = \sqrt{(1 - 4)^2 + (2 - 3)^2} \\[1em] = \sqrt{(-3)^2 + (-1)^2} \\[1em] = \sqrt{9 + 1} \\[1em] = \sqrt{10} \text{ units}. \\[1em] AD = \sqrt{(1 - 4)^2 + (2 - 5)^2} \\[1em] = \sqrt{3^2 + (-3)^2} \\[1em] = \sqrt{9 + 9} \\[1em] = \sqrt{18} \\[1em] = 3\sqrt{2} \text{ units}.\end{aligned}$$

Calculating diagonals :

$$\begin{aligned}AC = \sqrt{(4 - 4)^2 + (3 - 5)^2} \\[1em] = \sqrt{0 + (-2)^2} \\[1em] = \sqrt{4} \\[1em] = 2 \text{ units}. \\[1em] BD = \sqrt{(1 - 7)^2 + (2 - 6)^2}\\[1em] = \sqrt{(-6)^2 + (-4)^2} \\[1em] = \sqrt{36 + 16} \\[1em] = \sqrt{52} \text{ units}.\end{aligned}$$

Since, opposite sides are equal and diagonals are not equal.

Hence, (4, 5), (7, 6), (4, 3), (1, 2) are the vertices of a parallelogram.

24Exercise 18.4

Find the coordinates of the circumcentre of the triangle whose vertices are (8, 6), (8, -2) and (2, -2). Also, find its circumradius.

Show SolutionHide Solution↓

Let O(x, y) be the circumcentre of the circle.

Let A(8, 6), B(8, -2) and C(2, -2) be the vertices of the triangle.

OB = OC [Radii of same circle]

Find the coordinates of the circumcentre of the triangle whose vertices are (8, 6), (8, -2) and (2, -2). Also, find its circumradius. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

$$\begin{aligned}\Rightarrow \sqrt{(x - 8)^2 + [y - (-2)]^2} = \sqrt{(x - 2)^2 + [y - (-2)]^2} \\[1em] \Rightarrow \sqrt{x^2 + 64 - 16x + [y + 2]^2} = \sqrt{x^2 + 4 - 4x + [y + 2]^2}\end{aligned}$$

Squaring both sides we get,

$$\begin{aligned}\Rightarrow x^2 + 64 - 16x + [y + 2]^2 = x^2 + 4 - 4x + [y + 2]^2 \\[1em] \Rightarrow x^2 - x^2 + [y + 2]^2 - [y + 2]^2 + 64 - 4 = 16x - 4x \\[1em] \Rightarrow 12x = 60 \\[1em] \Rightarrow x = \frac{60}{12} \\[1em] \Rightarrow x = 5.\end{aligned}$$

Also,

OA = OB [Radii of same circle]

By distance formula,

$$\begin{aligned}\Rightarrow \sqrt{(x - 8)^2 + (y - 6)^2} = \sqrt{(x - 8)^2 + [y - (-2)]^2} \\[1em] \Rightarrow \sqrt{(x - 8)^2 + y^2 + 36 - 12y} = \sqrt{(x - 8)^2 + [y + 2]^2}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow (x - 8)^2 + y^2 + 36 - 12y = (x - 8)^2 + [y + 2]^2 \\[1em] \Rightarrow (x - 8)^2 + y^2 + 36 - 12y = (x - 8)^2 + y^2 + 4 + 4y \\[1em] \Rightarrow (x - 8)^2 - (x - 8)^2 + y^2 - y^2 + 4y + 12y = 36 - 4 \\[1em] \Rightarrow 16y = 32 \\[1em] \Rightarrow y = \frac{32}{16} \\[1em] \Rightarrow y = 2.\end{aligned}$$

O = (x, y) = (5, 2).

Radius = OA.

$$\begin{aligned}OA = \sqrt{(8 - 5)^2 + (6 - 2)^2} \\[1em] = \sqrt{3^2 + 4^2} \\[1em] = \sqrt{9 + 16} \\[1em] = \sqrt{25} \\[1em] = 5 \text{ units}.\end{aligned}$$

Hence, circumcenter = (5, 2) and circumradius = 5 units.

11 Mark · Multiple Choice Questions

Point (-3, 5) lies in the

Show SolutionHide Solution↓

In second quadrant,

x-coordinate is negative and y-coordinate is positive.

∴ P(-3, 5) lies in second quadrant.

Hence, Option 2 is the correct option.

21 Mark · Multiple Choice Questions

Point (0, -7) lies

Show SolutionHide Solution↓

x-coordinate of any point on y-axis = 0.

∴ P(0, -7) lies on y-axis.

Hence, Option 3 is the correct option.

31 Mark · Multiple Choice Questions

Abscissa of a point is positive in

Show SolutionHide Solution↓

Abscissa (or x-coordinate) is positive in I and IV quadrants.

Hence, Option 2 is the correct option.

41 Mark · Multiple Choice Questions

The point which lies on y-axis at a distance of 5 units in the negative direction of y-axis is

Show SolutionHide Solution↓

Let point be P(x, y).

Since,

Point lies on y-axis.

∴ x = 0.

Also, point is at a distance of 5 units in the negative direction of y-axis.

∴ y = -5.

P = (x, y) = (0, -5).

Hence, Option 3 is the correct option.

51 Mark · Multiple Choice Questions

If the perpendicular distance of a point P from the x-axis is 5 units and the foot of perpendicular lies on the negative direction of x-axis, then the point P has

Show SolutionHide Solution↓

In graph, let 1 block = 1 unit.

If the perpendicular distance of a point P from the x-axis is 5 units and the foot of perpendicular lies on the negative direction of x-axis, then the point P has? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Since,

Perpendicular distance of a point P from the x-axis is 5 units and the foot of perpendicular lies on the negative direction of x-axis.

Let foot of perpendicular be B.

So, position of point P can be A or C.

From graph,

The y-coordinate of A and C = 5 and -5.

Hence, Option 4 is the correct option.

61 Mark · Multiple Choice Questions

The points whose abscissa and ordinate have different signs will lie in

Show SolutionHide Solution↓

In second quadrant,

x-coordinate is negative and y-coordinate is positive.

In fourth quadrant,

x-coordinate is positive and y-coordinate is negative.

Hence, points having opposite signs lie in II and IV quadrants.

Hence, Option 4 is the correct option.

71 Mark · Multiple Choice Questions

The points (-5, 2) and (2, -5) lie in

Show SolutionHide Solution↓

In second quadrant,

x-coordinate is negative and y-coordinate is positive.

∴ (-5, 2) lies in II quadrant.

In fourth quadrant,

x-coordinate is positive and y-coordinate is negative.

∴ (2, -5) lies in IV quadrant.

Hence, Option 3 is the correct option.

81 Mark · Multiple Choice Questions

If P(-1, 1), Q(3, -4), R(1, -1), S(-2, -3) and T(-4, 4) are plotted on the graph paper, then point(s) in the fourth quadrant are

Show SolutionHide Solution↓

From graph,

If P(-1, 1), Q(3, -4), R(1, -1), S(-2, -3) and T(-4, 4) are plotted on the graph paper, then point(s) in the fourth quadrant are? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Q and R lies in fourth quadrant.

Hence, Option 2 is the correct option.

91 Mark · Multiple Choice Questions

On plotting the points O(0, 0), A(3, 0), B(3, 4), C(0, 4) and joining OA, AB, BC, and CO which of the following figure is obtained?

Show SolutionHide Solution↓

From graph,

On plotting the points O(0, 0), A(3, 0), B(3, 4), C(0, 4) and joining OA, AB, BC, and CO which of the following figure is obtained? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

OA = BC = 3 units

OC = AB = 4 units

∴ Figure obtained is a rectangle.

Hence, Option 2 is the correct option.

101 Mark · Multiple Choice Questions

Which of the following points lie on the graph of the equation :

3x - 5y + 7 = 0?

Show SolutionHide Solution↓

Substituting (1, -2) in L.H.S. of the equation 3x - 5y + 7 = 0, we get :

⇒ 3x - 5y + 7

⇒ 3(1) - 5(-2) + 7

⇒ 3 + 10 + 7

⇒ 20

Since, L.H.S. ≠ R.H.S., (1, -2) does not satisfy the equation.

Substituting (2, 1) in L.H.S. of the equation 3x - 5y + 7 = 0, we get :

⇒ 3x - 5y + 7

⇒ 3(2) - 5(1) + 7

⇒ 6 - 5 + 7

⇒ 8

Since, L.H.S. ≠ R.H.S., (2, 1) does not satisfy the equation.

Substituting (-1, 2) in L.H.S. of the equation 3x - 5y + 7 = 0, we get :

⇒ 3x - 5y + 7

⇒ 3(-1) - 5(2) + 7

⇒ -3 - 10 + 7

⇒ -6

Since, L.H.S. ≠ R.H.S., (-1, 2) does not satisfy the equation.

Substituting (1, 2) in L.H.S. of the equation 3x - 5y + 7 = 0, we get :

⇒ 3x - 5y + 7

⇒ 3(1) - 5(2) + 7

⇒ 3 - 10 + 7

⇒ 0

Since, L.H.S. = R.H.S., (1, 2) satisfies the equation.

Hence, Option 4 is the correct option.

111 Mark · Multiple Choice Questions

The pair of equation x = a and y = b graphically represents lines which are

Show SolutionHide Solution↓

From graph,

The pair of equation x = a and y = b graphically represents lines which are? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

x = a and y = b intersects at (a, b).

Hence, Option 4 is the correct option.

121 Mark · Multiple Choice Questions

The distance of the point P(2, 3) from the x-axis is

Show SolutionHide Solution↓

The distance between the point P(2, 3) and x-axis can be determined by assuming a point A(2, 0) on x-axis.

By distance formula,

$$\begin{aligned}\Rightarrow d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \Rightarrow AP = \sqrt{(2 - 2)^2 + (3 - 0)^2} \\[1em] \Rightarrow AP = \sqrt{0 + 3^2} \\[1em] \Rightarrow AP = \sqrt{9} \\[1em] \Rightarrow AP = 3 \text{ units}.\end{aligned}$$

Hence, Option 2 is the correct option.

131 Mark · Multiple Choice Questions

The distance of the point P(-4, 3) from the y-axis is

Show SolutionHide Solution↓

The distance between the point P(-4, 3) and y-axis can be determined by assuming a point A(0, 3) on y-axis.

By distance formula,

$$\begin{aligned}\Rightarrow d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \Rightarrow AP = \sqrt{(-4 - 0)^2 + (3 - 3)^2} \\[1em] \Rightarrow AP = \sqrt{(-4)^2 + 0} \\[1em] \Rightarrow AP = \sqrt{16} \\[1em] \Rightarrow AP = 4 \text{ units}.\end{aligned}$$

Hence, Option 3 is the correct option.

141 Mark · Multiple Choice Questions

The distance of the point P(-6, 8) from the origin is

Show SolutionHide Solution↓

Origin (O) = (0, 0) and P = (-6, 8).

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore OP = \sqrt{(-6 - 0)^2 + (8 - 0)^2} \\[1em] = \sqrt{(-6)^2 + 8^2} \\[1em] = \sqrt{36 + 64} \\[1em] = \sqrt{100} \\[1em] = 10 \text{ units}.\end{aligned}$$

Hence, Option 3 is the correct option.

151 Mark · Multiple Choice Questions

The distance between the points A(0, 6) and B(0, -2) is

Show SolutionHide Solution↓

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(0 - 0)^2 + (-2 - 6)^2} \\[1em] = \sqrt{0 + (-8)^2} \\[1em] = \sqrt{64} \\[1em] = 8 \text{ units}.\end{aligned}$$

Hence, Option 2 is the correct option.

161 Mark · Multiple Choice Questions

The distance between the points (0, 5) and (-5, 0) is

Show SolutionHide Solution↓

Let, A = (0, 5) and B = (-5, 0).

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(-5 - 0)^2 + (0 - 5)^2} \\[1em] = \sqrt{(-5)^2 + (-5)^2} \\[1em] = \sqrt{25 + 25} \\[1em] = \sqrt{50} \\[1em] = 5\sqrt{2}\text{ units}.\end{aligned}$$

Hence, Option 2 is the correct option.

171 Mark · Multiple Choice Questions

AOBC is a rectangle whose three vertices are A(0, 3), O(0, 0) and B(5, 0). The length of its diagonal is

Show SolutionHide Solution↓

Since, AOBC is the rectangle.

So, AB will be the diagonal.

AOBC is a rectangle whose three vertices are A(0, 3), O(0, 0) and B(5, 0). The length of its diagonal is? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(5 - 0)^2 + (0 - 3)^2} \\[1em] = \sqrt{(5)^2 + (-3)^2} \\[1em] = \sqrt{25 + 9} \\[1em] = \sqrt{34} \text{ units}.\end{aligned}$$

Hence, Option 3 is the correct option.

181 Mark · Multiple Choice Questions

If the distance between the points (2, -2) and (-1, x) is 5 units, then one of the value of x is

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Given,

Distance between (2, -2) and (-1, x) is 5 units.

$$\begin{aligned}\therefore 5 = \sqrt{(-1 - 2)^2 + [x - (-2)]^2} \\[1em] \Rightarrow 5 = \sqrt{(-3)^2 + [x + 2]^2} \\[1em] \Rightarrow 5 = \sqrt{9 + x^2 + 4 + 4x} \\[1em] \Rightarrow 5 = \sqrt{x^2 + 4x + 13} \\[1em] \Rightarrow x^2 + 4x + 13 = 5^2 \text{ [On squaring both sides]} \\[1em] \Rightarrow x^2 + 4x + 13 = 25 \\[1em] \Rightarrow x^2 + 4x - 12 = 0 \\[1em] \Rightarrow x^2 + 6x - 2x - 12 = 0 \\[1em] \Rightarrow x(x + 6) - 2(x + 6) = 0 \\[1em] \Rightarrow (x - 2)(x + 6) = 0 \\[1em] \Rightarrow x - 2 = 0 \text{ or } x + 6 = 0 \\[1em] \Rightarrow x = 2 \text{ or } x = -6.\end{aligned}$$

As distance cannot be negative,

∴ x = 2

Hence, Option 2 is the correct option.

191 Mark · Multiple Choice Questions

The distance between the points (4, p) and (1, 0) is 5 units, then the value of p is

Show SolutionHide Solution↓

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Given,

Distance between (4, p) and (1, 0) is 5 units.

$$\begin{aligned}\therefore 5 = \sqrt{(1 - 4)^2 + (0 - p)^2} \\[1em] \Rightarrow 5 = \sqrt{(-3)^2 + (-p)^2} \\[1em] \Rightarrow 5 = \sqrt{9 + p^2} \\[1em] \Rightarrow p^2 + 9 = 5^2 \text{ [On squaring both sides]} \\[1em] \Rightarrow p^2 + 9 = 25 \\[1em] \Rightarrow p^2 = 16 \\[1em] \Rightarrow p = \sqrt{16} \\[1em] \Rightarrow p = \pm 4.\end{aligned}$$

Hence, Option 3 is the correct option.

201 Mark · Multiple Choice Questions

The points (-4, 0), (4, 0) and (0, 3) are the vertices of a

Show SolutionHide Solution↓

Let A = (-4, 0), B = (4, 0) and C = (0, 3).

The points (-4, 0), (4, 0) and (0, 3) are the vertices of a? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{[4 - (-4)]^2 + (0 - 0)^2} \\[1em] = \sqrt{[4 + 4]^2 + 0^2} \\[1em] = \sqrt{8^2} \\[1em] = \sqrt{64} \\[1em] = 8 \text{ units} \\[1em] \therefore BC = \sqrt{(0 - 4)^2 + (3 - 0)^2} \\[1em] = \sqrt{(-4)^2 + 3^2} \\[1em] = \sqrt{16 + 9} \\[1em] = \sqrt{25} \\[1em] = 5 \text{ units} \\[1em] \therefore AC = \sqrt{[0 - (-4)]^2 + (3 - 0)^2} \\[1em] = \sqrt{4^2 + 3^2} \\[1em] = \sqrt{16 + 9} \\[1em] = \sqrt{25} \\[1em] = 5 \text{ units} \\[1em]\end{aligned}$$

Since, AC = BC.

∴ ABC is an isosceles triangle.

Hence, Option 2 is the correct option.

211 Mark · Multiple Choice Questions

The area of a square whose vertices are A(0, -2), B(3, 1), C(0, 4) and D(-3, 1) is

Show SolutionHide Solution↓

By distance formula,

The area of a square whose vertices are A(0, -2), B(3, 1), C(0, 4) and D(-3, 1) is? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(3 - 0)^2 + [1 - (-2)]^2} \\[1em] = \sqrt{3^2 + [1 + 2]^2} \\[1em] = \sqrt{9 + 3^2} \\[1em] = \sqrt{9 + 9} \\[1em] = \sqrt{18} \\[1em] = 3\sqrt{2}.\end{aligned}$$

Area of square = (side)2 = AB2

= $(3\sqrt{2})^2$ = 18 sq. units.

Hence, Option 1 is the correct option.

221 Mark · Multiple Choice Questions

In the adjoining figure, the area of triangle ABC is

In the adjoining figure, the area of triangle ABC is? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.
Show SolutionHide Solution↓

Draw a perpendicular AD from A on x-axis.

In the adjoining figure, the area of triangle ABC is? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

D = (1, 0).

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AD = \sqrt{(1 - 1)^2 + (0 - 3)^2} \\[1em] = \sqrt{0 + (-3)^2} \\[1em] = \sqrt{9} \\[1em] = 3 \text{ units}. \\[1em] \therefore BC = \sqrt{[4 - (-1)]^2 + (0 - 0)^2} \\[1em] = \sqrt{[4 + 1]^2 + 0} \\[1em] = \sqrt{5^2} \\[1em] = \sqrt{25} \\[1em] = 5 \text{ units}.\end{aligned}$$

Area of triangle = $\frac{1}{2} \times$ base × height

= $\frac{1}{2} \times 3 \times 5$

= $\frac{15}{2}$ = 7.5 sq. units

Hence, Option 3 is the correct option.

231 Mark · Multiple Choice Questions

The perimeter of a triangle with vertices (0, 4), (0, 0) and (3, 0) is

Show SolutionHide Solution↓

Let A(0, 4), B(0, 0) and C(3, 0) be the vertices of the triangle.

The perimeter of a triangle with vertices (0, 4), (0, 0) and (3, 0) is? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(0 - 0)^2 + (0 - 4)^2} \\[1em] = \sqrt{0 + (-4)^2} \\[1em] = \sqrt{16} \\[1em] = 4 \text{ units}. \\[1em] \therefore BC = \sqrt{(3 - 0)^2 + (0 - 0)^2} \\[1em] = \sqrt{3^2 + 0} \\[1em] = \sqrt{9} \\[1em] = 3 \text{ units} \\[1em] \therefore AC = \sqrt{(3 - 0)^2 + (0 - 4)^2} \\[1em] = \sqrt{3^2 + (-4)^2} \\[1em] = \sqrt{9 + 16} \\[1em] = 5 \text{ units}.\end{aligned}$$

Perimeter = AB + BC + AC = 4 + 3 + 5 = 12 units.

Hence, Option 2 is the correct option.

241 Mark · Multiple Choice Questions

If A is a point on the y-axis whose ordinate is 5 and B is the point (-3, 1), then the length of AB is

Show SolutionHide Solution↓

Since, A is a point on y-axis, so x-coordinate = 0.

A = (0, 5).

B = (-3, 1).

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] = \sqrt{(-3 - 0)^2 + (1 - 5)^2} \\[1em] = \sqrt{(-3)^2 + (-4)^2} \\[1em] = \sqrt{9 + 16} \\[1em] = \sqrt{25} \\[1em] = 5 \text{ units}.\end{aligned}$$

Hence, Option 2 is the correct option.

251 Mark · Multiple Choice Questions

The points A(9, 0), B(9, 6), C(-9, 6) and D(-9, 0) are the vertices of a

Show SolutionHide Solution↓

By distance formula,

The points A(9, 0), B(9, 6), C(-9, 6) and D(-9, 0) are the vertices of a? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(9 - 9)^2 + (6 - 0)^2} \\[1em] = \sqrt{0 + 6^2} \\[1em] = \sqrt{36} \\[1em] = 6 \text{ units}. \\[1em] \therefore BC = \sqrt{(-9 - 9)^2 + (6 - 6)^2} \\[1em] = \sqrt{(-18)^2 + 0} \\[1em] = \sqrt{324} \\[1em] = 18 \text{ units}. \\[1em] \therefore CD = \sqrt{[-9 - (-9)]^2 + (0 - 6)^2} \\[1em] = \sqrt{[-9 + 9]^2 + (-6)^2} \\[1em] = \sqrt{0 + 36} \\[1em] = \sqrt{36} \\[1em] = 6 \text{ units}. \\[1em] \therefore AD = \sqrt{(-9 - 9)^2 + (0 - 0)^2} \\[1em] = \sqrt{(-18)^2 + 0} \\[1em] = \sqrt{324} \\[1em] = 18 \text{ units}.\end{aligned}$$

Since, AB = CD and BC = AD.

∴ ABCD is a rectangle.

Hence, Option 1 is the correct option.

261 Mark · Multiple Choice Questions

Consider the following two statements:

Statement 1: The point (x2, y) lies on the y - axis. Then the value of x is zero.

Statement 2: The abscissa of every point on y-axis is zero.

Which of the following is valid?

Show SolutionHide Solution↓

Any point that lies on the y-axis has its x-coordinate equal to zero.

The given point is (x2, y).

For this point to lie on the y-axis, its x-coordinate, which is x2, must be equal to zero.

So, x2 = 0.

If x2 = 0, then x must be 0.

∴ Statement 1 is true.

The abscissa is the x-coordinate of a point in a Cartesian coordinate system.

All points on the y-axis are of the form (0, y), where y can be any real number.

For any point on the y-axis, its x-coordinate (abscissa) is 0.

∴ Statement 2 is true.

∴ Both the statements are true.

Hence, option 1 is correct option.

1Assertion Reason Type Questions

Assertion (A): Two ordered pairs (a, b) and (c, d) are equal if a = c and b = d.

Reason (R): If a ≠ b, then (a, b) ≠ (b, a).

Show SolutionHide Solution↓

Two ordered pairs (a, b) and (c, d) are equal if a = c and b = d.

This statement is the definition of equality for ordered pairs. For two ordered pairs to be considered equal, their corresponding elements must be equal.

So, (a, b) = (c, d) if and only if a = c and b = d.

∴ Assertion (A) is true.

If a ≠ b, then (a, b) ≠ (b, a).

For example, the ordered pair (2, 3) is not the same as (3,2). They represent different points in a coordinate plane.

∴ Reason (R) is true.

∴ Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct reason (or explanation) for Assertion (A).

Hence, option 4 is the correct option.

2Assertion Reason Type Questions

Assertion (A): The point P(3, -5) lies in quadrant II and the point Q(-2, -1) lies in quadrant III.

Reason (R): The signs of a point in I, II, III and IV quadrants are respectively (+, +), (-, +), (-, -) and (+, -).

Show SolutionHide Solution↓

Point P(3, -5):

The x-coordinate is positive, and the y-coordinate is negative.

A point with a positive x-coordinate and a negative y-coordinate lies in quadrant IV.

Point Q(-2, -1):

The x-coordinate is negative, and the y-coordinate is negative.

A point with a negative x-coordinate and a negative y-coordinate lies in quadrant III.

∴ Assertion (A) is false.

Quadrant I: x-coordinate is positive, y-coordinate is positive (+, +).

Quadrant II: x-coordinate is negative, y-coordinate is positive (-, +).

Quadrant III: x-coordinate is negative, y-coordinate is negative (-, -).

Quadrant IV: x-coordinate is positive, y-coordinate is negative (+, -).

∴ Reason (R) is true.

∴ Assertion (A) is false, Reason (R) is true.

Hence, option 2 is the correct option.

3Assertion Reason Type Questions

Assertion (A): Two points A and B having coordinates (3, 3) and (-3, -3) respectively are joined. The line segment AB passes through the origin.

Reason (R): Origin is the point of intersection of the coordinate axes.

Show SolutionHide Solution↓

When a point (x,y) is reflected across the origin (0, 0), its new coordinates become (−x, −y). This transformation is also known as point symmetry with respect to the origin.

Point A has coordinates (3, 3).

If we reflect point A(3, 3) across the origin (0, 0), the coordinates of its reflected image would be (−3, −3).

The coordinates of the given point B are exactly (−3, −3).

Since point B is the exact reflection of point A across the origin, it means that the origin (0, 0) lies precisely on the straight line segment connecting point A and point B.

Therefore, the line segment AB passes through the origin.

∴ Assertion (A) is true.

Origin is the point of intersection of the coordinate axes.

This is the definition of the origin in a Cartesian coordinate system. It's the point where the x-axis and y-axis intersect, and its coordinates are (0, 0).

∴ Reason (R) is true.

∴ Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct reason (or explanation) for Assertion (A).

Hence, option 4 is the correct option.

4Assertion Reason Type Questions

Assertion (A): If the points A(2, 9), B(2, 5) and C(5, 5) are joined, then ΔABC is right angled.

Reason (R): If AC2 = AB2 + BC2, then ∠B = 90°.

Show SolutionHide Solution↓

Given, the points A(2, 9), B(2, 5) and C(5, 5).

By distance formula,

Distance between two points = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Given, points A(2, 9), B(2, 5) and C(5, 5).

$$\begin{aligned}\text{Distance between AB }= \sqrt{(2 - 2)^2 + (5 - 9)^2} \\[1em] = \sqrt{0 + (-4)^2} \\[1em] = \sqrt{0 + 16} \\[1em] = \sqrt{16} \\[1em] = \text{4 units}. \\[1em] \text{Distance between BC } = \sqrt{(5 - 2)^2 + (5 - 5)^2} \\[1em] = \sqrt{3^2 + 0^2} \\[1em] = \sqrt{9 + 0} \\[1em] = \sqrt{9} \\[1em] = \text{3 units}. \\[1em] \text{Distance between AC } = \sqrt{(5 - 2)^2 + (5 - 9)^2} \\[1em] = \sqrt{3^2 + (-4)^2} \\[1em] = \sqrt{9 + 16} \\[1em] = \sqrt{25} \\[1em] = \text{5 units}.\end{aligned}$$

AC2 = 52 = 25 units

AB2 = 42 = 16 units

BC2 = 32 = 9 units

Since, AC2 = AB2 + BC2, thus it satisfies pythagoras theorem.

Thus, ABC is a right angled triangle at B.

Thus, Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct reason for Assertion (A).

Hence, option 3 is the correct option.

5Assertion Reason Type Questions

Assertion (A): Point (0, 9) is a point on y-axis which is equidistant from points (6, 5) and (-4, 3).

Reason (R): Abscissa of a point on y-axis is 0.

Show SolutionHide Solution↓

A point lies on the y-axis if and only if its x-coordinate (abscissa) is 0.

∴ Reason (R) is true.

Let P = (0, 9), A = (6, 5), and B = (-4, 3).

By formula,

Distance between two points = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

$$\begin{aligned}PA = \sqrt{(6 - 0)^2 + (5 - 9)^2}\\[1em] = \sqrt{6^2 + (-4)^2}\\[1em] = \sqrt{36 + 16}\\[1em] = \sqrt{52}. \\[1em] PB = \sqrt{(-4 - 0)^2 + (3 - 9)^2}\\[1em] = \sqrt{(-4)^2 + (-6)^2}\\[1em] = \sqrt{16 + 36}\\[1em] = \sqrt{52}\end{aligned}$$

Since PA = PB = $\sqrt{52}$.

​Therefore, the point (0, 9) is a point on y-axis which is equidistant from (6, 5) and (-4, 3).

∴ Assertion (A) is true.

∴ Both Assertion (A) and Reason (R) are true, and Reason (R) is not the correct reason (or explanation) for Assertion (A).

Hence, option 4 is the correct option.

1Chapter Test

Three vertices of a rectangle are A(2, -1), B(2, 7) and C(4, 7). Plot these points on a graph and hence use it to find the co-ordinates of the fourth vertex D. Also find the co-ordinates of

(i) the mid-point of BC

(ii) the mid-point of CD

(iii) the point of intersection of the diagonals.

What is the area of the rectangle ?

Show SolutionHide Solution↓

In graph,

1 block = 1 unit.

Steps of construction :

  1. Plot the points A(2, -1), B(2, 7) and C(4, 7) on graph.

  2. Join AB and BC.

  3. Measure AB. Draw a line segment CD, from point C parallel to y-axis.

  4. Measure BC. Draw a line segment AD, from point A parallel to x-axis.

  5. Mark F and G mid-point of BC and CD respectively.

  6. Join AC and BD diagonals of rectangle.

  7. Mark E as the point of intersection of diagonals.

Three vertices of a rectangle are A(2, -1), B(2, 7) and C(4, 7). Plot these points on a graph and hence use it to find the co-ordinates of the fourth vertex D. Also find the co-ordinates of (i) the mid-point of BC (ii) the mid-point of CD (iii) the point of intersection of the diagonals. What is the area of the rectangle ? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

Coordinates of D = (4, -1).

(i) From graph,

F is the mid-point of BC and F = (3, 7).

Hence, coordinates of mid-point of BC = (3, 7).

(ii) From graph,

G is the mid-point of CD and G = (4, 3).

Hence, coordinates of mid-point of CD = (4, 3).

(iii) From graph,

E is the point of intersection of diagonals.

Hence, point of intersection of the diagonals = (3, 3).

From graph,

AB = 8 units and BC = 2 units.

Area of the rectangle ABCD = length × breadth

= AB × BC

= 8 × 2

= 16 sq. units.

Hence, the area of the rectangle = 16 sq. units.

2Chapter Test

Three vertices of a parallelogram are A(3, 5), B(3, -1) and C(-1, -3). Plot these points on a graph paper and hence use it to find the coordinates of the fourth vertex D. Also find the coordinates of the mid-point of the side CD. What is the area of the parallelogram?

Show SolutionHide Solution↓

Steps of construction :

  1. Plot the points A(3, 5), B(3, -1) and C(-1, -3) on graph paper.

  2. Join AB and BC.

  3. From C draw a line CD parallel to AB, such that CD = AB.

  4. From A draw a line AD parallel to BC, such that AD = BC.

  5. Mark E, the mid-point of CD.

Three vertices of a parallelogram are A(3, 5), B(3, -1) and C(-1, -3). Plot these points on a graph paper and hence use it to find the coordinates of the fourth vertex D. Also find the coordinates of the mid-point of the side CD. What is the area of the parallelogram? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

The coordinates of fourth vertex D are (-1, 3).

The coordinates of the midpoint of CD i.e. E are (-1, 0).

As, 1 block = 1 unit

EF = 4 units

CD = 6 units

Area of parallelogram ABCD = Base × height

= CD × EF

= 6 × 4

= 24 sq. units.

Hence, D = (-1, 3), coordinates of mid-point of CD = (-1, 0) and the area of the parallelogram is 24 sq. units.

3(i)Chapter Test

Draw the graphs of the following linear equation.

y = 2x - 1

Also find slope and y-intercept of this line.

Show SolutionHide Solution↓

Given,

y = 2x - 1 ..........(1)

When x = 1, y = 2 × 1 - 1 = 2 - 1 = 1

x = 2, y = 2 × 2 - 1 = 4 - 1 = 3

x = 3, y = 2 × 3 - 1 = 6 - 1 = 5.

x123
y135

Steps of construction :

  1. Plot the points (1, 1), (2, 3) and (3, 5) on graph.

  2. Join the points.

Draw the graphs of the following linear equation. y = 2x - 1. Also find slope and y-intercept of this line. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Comparing equation (1) with y = mx + c, we get :

m = 2 and c = -1.

Hence, slope of the line = 2 and y-intercept = -1.

3(ii)Chapter Test

Draw the graphs of the following linear equation.

2x + 3y = 6

Also find slope and y-intercept of this line.

Show SolutionHide Solution↓

Given,

⇒ 2x + 3y = 6

⇒ 3y = 6 - 2x

⇒ y = $\frac{6}{3} - \frac{2x}{3}$

⇒ y = $-\frac{2x}{3} + 2$ ...........(1)

When x = 0, $y = 2 - \frac{2x}{3} = 2 - \frac{2 \times 0}{3}$ = 2 - 0 = 2,

x = 3, y = $2 - \frac{2 \times 3}{3}$ = 2 - 2 = 0,

x = 6, y = $2 - \frac{2 \times 6}{3} = 2 - \frac{12}{3}$ = 2 - 4 = -2.

x036
y20-2

Steps of construction :

  1. Plot the points (0, 2), (3, 0) and (6, -2) on graph.

  2. Join the points.

Draw the graphs of the following linear equation. 2x + 3y = 6. Also find slope and y-intercept of this line. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Comparing equation (1) with y = mx + c, we get :

m = $-\frac{2}{3}$ and c = 2.

Hence the slope of the line = $-\frac{2}{3}$ and y intercept = 2.

3(iii)Chapter Test

Draw the graphs of the following linear equation.

2x - 3y = 4

Also find slope and y-intercept of this line.

Show SolutionHide Solution↓

Given,

⇒ 2x - 3y = 4

⇒ 3y = 2x - 4

⇒ y = $\frac{2x - 4}{3}$

⇒ y = $\frac{2}{3}x - \frac{4}{3}$ ........(1)

When x = -1, y = $\frac{2}{3} \times -1 - \frac{4}{3} = -\frac{2}{3} - \frac{4}{3} = -\frac{6}{3}$ = -2,

x = 2, y = $\frac{2}{3} \times 2 - \frac{4}{3} = \frac{4}{3} - \frac{4}{3}$ = 0,

x = 5, y = $\frac{2}{3} \times 5 - \frac{4}{3} = \frac{10}{3} - \frac{4}{3} = \frac{6}{3}$ = 2.

x-125
y-202

Steps of construction :

  1. Plot the points (-1, -2), (2, 0) and (5, 2) on graph.

  2. Join the points.

Draw the graphs of the following linear equation. 2x - 3y = 4. Also find slope and y-intercept of this line. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Comparing equation (1) with y = mx + c.

m = $\frac{2}{3}$ and c = $-\frac{4}{3}$.

Hence, the slope of line = $\frac{2}{3}$ and y intercept = $-\frac{4}{3}$.

4Chapter Test

Draw the graph of the equation 3x - 4y = 12. From the graph, find :

(i) the value of y when x = -4

(ii) the value of x when y = 3.

Show SolutionHide Solution↓

Given,

⇒ 3x - 4y = 12

⇒ 4y = 3x - 12

⇒ y = $\frac{3x - 12}{4}$

⇒ y = $\frac{3}{4}x - 3$.

When x = 0, y = $\frac{3}{4} \times 0 - 3$ = 0 - 3 = -3,

x = 4, y = $\frac{3}{4} \times 4 - 3$ = 3 - 3 = 0,

x = 8, y = $\frac{3}{4} \times 8 - 3 = \frac{24}{4} - 3$ = 6 - 3 = 3.

x048
y-303

Steps of construction :

  1. Plot the points (0, -3), (4, 0) and (8, 3) on graph.

  2. Join the points.

Draw the graph of the equation 3x - 4y = 12. From the graph, find : (i) the value of y when x = -4 (ii) the value of x when y = 3. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

(i) Steps of construction :

  1. Take a point N (x = -4) and draw a line parallel to y-axis, touching the graph at point M.

  2. From M draw a line parallel to x-axis touching y-axis at point O (y = -6).

Hence, when x = -4, the value of y is -6.

(ii) Steps of construction :

  1. Take a point P (y = 3) and draw a line parallel to x-axis, touching the graph at point R.

  2. From R draw a line parallel to y-axis touching x-axis at point Q (x = 8).

Hence, when y = 3, the value of x is 8.

5Chapter Test

Solve graphically, the simultaneous equations : 2x - 3y = 7; x + 6y = 11.

Show SolutionHide Solution↓

Given,

⇒ 2x - 3y = 7

⇒ 3y = 2x - 7

⇒ y = $\frac{2x - 7}{3}$ .........(1)

When, x = -1, y = $\frac{2 \times -1 - 7}{3} = \frac{-2 - 7}{3} = -\frac{9}{3}$ = -3,

x = 2, y = $\frac{2 \times 2 - 7}{3} = \frac{4 - 7}{3} = -\frac{3}{3}$ = -1,

x = 5, y = $\frac{2 \times 5 - 7}{3} = \frac{10 - 7}{3} = \frac{3}{3}$ = 1.

Table of values of equation (1) :

x-125
y-3-11

Steps of construction :

  1. Plot the points (-1, -3), (2, -1) and (5, 1) on graph.

  2. Join the points.

Given,

⇒ x + 6y = 11

⇒ 6y = 11 - x

⇒ y = $\frac{11 - x}{6}$ ..........(2)

When x = -7, y = $\frac{11 - (-7)}{6} = \frac{18}{6}$ = 3,

x = -1, y = $\frac{11 - (-1)}{6} = \frac{12}{6}$ = 2,

x = 5, y = $\frac{11 - 5}{6} = \frac{6}{6}$ = 1.

Table of values of equation (2) :

x-7-15
y321

Steps of construction :

  1. Plot the points (-7, 3), (-1, 2) and (5, 1) on graph.

  2. Join the points.

Solve graphically, the simultaneous equations : 2x - 3y = 7; x + 6y = 11. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

The two lines intersect at P(5, 1).

Hence x = 5, y = 1.

6Chapter Test

Solve the following system of equations graphically :

x - 2y - 4 = 0, 2x + y - 3 = 0.

Show SolutionHide Solution↓

Given,

⇒ x - 2y - 4 = 0

⇒ 2y = x - 4

⇒ y = $\frac{x - 4}{2}$ .........(1)

When x = -2, y = $\frac{-2 - 4}{2} = -\frac{6}{2}$ = -3,

x = 0, y = $\frac{0 - 4}{2} = -\frac{4}{2} = -2$,

x = 2, y = $\frac{2 - 4}{2} = -\frac{2}{2}$ = -1.

Table of values of equation (1) :

x-202
y-3-2-1

Steps of construction :

  1. Plot the points (-2, -3), (0, -2) and (2, -1) on graph.

  2. Join the points.

Given,

⇒ 2x + y - 3 = 0

⇒ y = 3 - 2x .........(2)

When x = 0, y = 3 - 2(0) = 3 - 0 = 3,

x = 1, y = 3 - 2(1) = 3 - 2 = 1,

x = 2, y = 3 - 2(2) = 3 - 4 = -1.

Table of values of equation (2) :

x012
y31-1

Steps of construction :

  1. Plot the points (0, 3), (1, 1) and (2, -1) on graph.

  2. Join the points.

Solve the following system of equations graphically : x - 2y - 4 = 0, 2x + y - 3 = 0. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

The lines intersect each other at P(2, -1).

Hence, x = 2, y = -1.

7Chapter Test

Using a scale of 1 cm to 1 unit for both the axes, draw the graphs of the following equations: 6y = 5x + 10, y = 5x - 15. From the graph, find

(i) the coordinates of the point where the two lines intersect.

(ii) the area of the triangle between the lines and the x-axis.

Show SolutionHide Solution↓

(i) Given,

⇒ 6y = 5x + 10

⇒ y = $\frac{5x + 10}{6}$ .........(1)

When x = 1, y = $\frac{5 \times 1 + 10}{6} = \frac{15}{6}$ = 2.5

x = -2, y = $\frac{5 \times -2 + 10}{6} = \frac{-10 + 10}{6} = \frac{0}{6}$ = 0,

x = 4, y = $\frac{5 \times 4 + 10}{6} = \frac{20 + 10}{6} = \frac{30}{6}$ = 5.

Table of values of equation (1) :

x1-24
y2.505

Steps of construction :

  1. Plot the points (1, 2.5), (-2, 0) and (4, 5) on graph.

  2. Join the points.

Using a scale of 1 cm to 1 unit for both the axes, draw the graphs of the following equations: 6y = 5x + 10, y = 5x - 15. From the graph, find (i) the coordinates of the point where the two lines intersect. (ii) the area of the triangle between the lines and the x-axis. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Given,

y = 5x - 15

When x = 2.5, y = 5 × 2.5 - 15 = 12.5 - 15 = -2.5,

x = 3, y = 5 × 3 - 15 = 15 - 15 = 0,

x = 4, y = 5 × 4 - 15 = 20 - 15 = 5.

Table of values of equation (2) :

x2.534
y-2.505

Steps of construction :

  1. Plot the points (2.5, -2.5), (3, 0) and (4, 5) on graph.

  2. Join the points.

From graph,

The lines intersect at point P(4, 5).

Hence, x = 4, y = 5.

(ii) From graph,

Triangle = PQR.

Draw a line PJ, from P perpendicular to x-axis.

PJ = 5 units

QR = 5 units

Area of triangle = $\frac{1}{2}$ × base × height

= $\frac{1}{2}$ × QR × PJ

= $\frac{1}{2}$ × 5 × 5

= $\frac{25}{2}$

= 12.5 sq. units.

Hence, area = 12.5 sq. units.

8Chapter Test

Find, graphically, the coordinates of the vertices of the triangle formed by the lines:

8y - 3x + 7 = 0, 2x - y + 4 = 0 and 5x + 4y = 29.

Show SolutionHide Solution↓

Given,

⇒ 8y - 3x + 7 = 0

⇒ 8y = 3x - 7

⇒ y = $\frac{3x - 7}{8}$ .........(1)

When x = -3, y = $\frac{3 \times -3 - 7}{8} = \frac{-9 - 7}{8} = -\frac{16}{8}$ = -2,

x = 1, y = $\frac{3 \times 1 - 7}{8} = \frac{3 - 7}{8} = -\frac{4}{8}$ = -0.5

x = 5, y = $\frac{3 \times 5 - 7}{8} = \frac{15 - 7}{8} = \frac{8}{8}$ = 1.

Table of values of equation (1) :

x-315
y-2-0.51

Steps of construction :

  1. Plot the points (-3, -2), (1, -0.5), (5, 1) on graph.

  2. Join the points.

Given,

⇒ 2x - y + 4 = 0

⇒ y = 2x + 4

When x = -2, y = 2(-2) + 4 = -4 + 4 = 0,

x = -1, y = 2(-1) + 4 = -2 + 4 = 2,

x = 0, y = 2(0) + 4 = 0 + 4 = 4.

Table of values of equation (2) :

x-2-10
y024

Steps of construction :

  1. Plot the points (-2, 0), (-1, 2), (0, 4) on graph.

  2. Join the points.

Given,

⇒ 5x + 4y = 29

⇒ 4y = 29 - 5x

⇒ y = $\frac{29 - 5x}{4}$ ..........(3)

When x = 1, y = $\frac{29 - 5 \times 1}{4} = \frac{29 - 5}{4} = \frac{24}{4}$ = 6,

x = 3, y = $\frac{29 - 5 \times 3}{4} = \frac{29 - 15}{4} = \frac{14}{4}$ = 3.5,

x = 5, y = $\frac{29 - 5 \times 5}{4} = \frac{29 - 25}{4} = \frac{4}{4}$ = 1.

Table of values of equation (3) :

x135
y63.51

Steps of construction :

  1. Plot the points (1, 6), (3, 3.5), (5, 1) on graph.

  2. Join the points.

Find, graphically, the coordinates of the vertices of the triangle formed by the lines: 8y - 3x + 7 = 0, 2x - y + 4 = 0 and 5x + 4y = 29. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

These three lines intersect each other at (-3, -2), (5, 1) and (1, 6).

Hence, the coordinates of the vertices of the triangle formed by these lines are (-3, -2), (5, 1) and (1, 6).

9Chapter Test

Find graphically the coordinates of the vertices of the triangle formed by the lines y - 2 = 0, 2y + x = 0 and y + 1 = 3 (x - 2). Hence, find the area of the triangle formed by these lines.

Show SolutionHide Solution↓

Given,

⇒ y - 2 = 0

⇒ y = 2 ........(1)

Given,

⇒ 2y + x = 0

⇒ 2y = -x

⇒ y = -$\frac{x}{2}$ ............(2)

When, x = -2, y = $-\frac{-2}{2}$ = 1,

x = 0, y = $-\frac{0}{2}$ = 0,

x = 2, y = $-\frac{2}{2}$ = -1.

Table of equation (2) :

x-202
y10-1

Steps of construction :

  1. Plot the points (-2, 1), (0, 0), (2, -1) on graph.

  2. Join the points.

Given,

⇒ y + 1 = 3(x - 2)

⇒ y + 1 = 3x - 6

⇒ y = 3x - 6 - 1

⇒ y = 3x - 7 ...........(3)

When x = 1, y = 3 × 1 - 7 = 3 - 7 = -4,

x = 2, y = 3 × 2 - 7 = 6 - 7 = -1,

x = 3, y = 3 × 3 - 7 = 9 - 7 = 2.

Table of equation (3) :

x123
y-4-12

Steps of construction :

  1. Plot the points (1, -4), (2, -1), (3, 2) on graph.

  2. Join the points.

Find graphically the coordinates of the vertices of the triangle formed by the lines y - 2 = 0, 2y + x = 0 and y + 1 = 3 (x - 2). Hence, find the area of the triangle formed by these lines. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

From graph,

A(-4, 2), B(3, 2), C(2, -1) are the vertices of the triangle.

From C, draw CD perpendicular to AB.

As, 1 block = 1 unit.

AB = 7 units and CD = 3 units

Area of triangle = $\frac{1}{2}$ × base × height

= $\frac{1}{2}$ × AB × CD

= $\frac{1}{2}$ × 7 × 3

= $\frac{21}{2}$ = 10.5 sq. units

Hence, coordinates of the vertices of the triangle are (-4, 2), (3, 2), (2, -1) and area = 10.5 sq. units.

10Chapter Test

A line segment is of length 10 units and one of its end is (-2, 3). If the ordinate of the other end is 9, find the abscissa of the other end.

Show SolutionHide Solution↓

Given,

Ordinate of the point on the other end = 9.

Let abscissa = x.

Given,

Distance between the two ends (-2, 3) and (x, 9) = 10 units.

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore \sqrt{[x - (-2)]^2 + (9 - 3)^2} = 10 \\[1em] \Rightarrow \sqrt{[x + 2]^2 + 6^2} = 10 \\[1em] \Rightarrow \sqrt{x^2 + 4 + 4x + 36} = 10 \\[1em] \Rightarrow x^2 + 4x + 40 = 100\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow x^2 + 4x + 40 - 100 = 0 \\[1em] \Rightarrow x^2 + 4x - 60 = 0\\[1em] \Rightarrow x^2 + 10x - 6x - 60 = 0 \\[1em] \Rightarrow x(x + 10) - 6(x + 10) = 0 \\[1em] \Rightarrow (x - 6)(x + 10) = 0 \\[1em] \Rightarrow x - 6 = 0 \text{ or } x + 10 = 0 \\[1em] \Rightarrow x = 6 \text{ or } x = -10.\end{aligned}$$

Hence, abscissa of other end = 6 or -10.

11Chapter Test

A(-4, -1), B(-1, 2) and C(α, 5) are the vertices of an isosceles triangle. Find the value of α given that AB is the unequal side.

Show SolutionHide Solution↓

It is given that

A(-4, -1), B(-1, 2) and C(α, 5) are the vertices of an isosceles triangle and AB is the unequal side.

∴ AC = BC.

A(-4, -1), B(-1, 2) and C(α, 5) are the vertices of an isosceles triangle. Find the value of α given that AB is the unequal side. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

$d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Since, AC = BC

$$\begin{aligned}\Rightarrow \sqrt{[α - (-4)]^2 + [5 - (-1)]^2} = \sqrt{[α - (-1)]^2 + [5 - 2]^2} \\[1em] \Rightarrow \sqrt{[α + 4]^2 + [5 + 1]^2} = \sqrt{[α + 1]^2 + [3]^2} \\[1em] \Rightarrow \sqrt{α^2 + 16 + 8α + 6^2} = \sqrt{α^2 + 1 + 2α + 9}\end{aligned}$$

On squaring both sides we get,

$$\begin{aligned}\Rightarrow α^2 + 16 + 8α + 6^2 = α^2 + 1 + 2α + 9 \\[1em] \Rightarrow α^2 + 8α + 16 + 36 = α^2 + 2α + 10 \\[1em] \Rightarrow α^2 - α^2 + 8α - 2α = 10 - 16 - 36 \\[1em] \Rightarrow 6α = -42 \\[1em] \Rightarrow α = -\frac{42}{6} \\[1em] \Rightarrow α = -7.\end{aligned}$$

Hence, α = -7.

12Chapter Test

If A(-3, 2), B(α, β) and C(-1, 4) are the vertices of an isosceles triangle, prove that α + β = 1, given AB = BC.

Show SolutionHide Solution↓

Given,

A(-3, 2), B(α, β) and C(-1, 4) are the vertices of an isosceles triangle

By distance formula,

If A(-3, 2), B(α, β) and C(-1, 4) are the vertices of an isosceles triangle, prove that α + β = 1, given AB = BC. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

$d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

As, AB = BC

$\therefore \sqrt{[α - (-3)]^2 + (β - 2)^2} = \sqrt{(-1 - α)^2 + (4 - β)^2}$

On squaring both sides,

$$\begin{aligned}\Rightarrow [α - (-3)]^2 + (β - 2)^2 = (-1 - α)^2 + (4 - β)^2 \\[1em] \Rightarrow [α + 3]^2 + (β - 2)^2 = (-1 - α)^2 + (4 - β)^2 \\[1em] \Rightarrow α^2 + 3^2 + 6α + β^2 + 4 - 4β = 1 + α^2 + 2α + 16 + β^2 - 8β \\[1em] \Rightarrow α^2 + 9 + 6α + β^2 + 4 - 4β = α^2 + 2α + 17 + β^2 - 8β \\[1em] \Rightarrow α^2 - α^2 + β^2 - β^2 + 6α - 2α - 4β + 8β = 17 - 9 - 4 \\[1em] \Rightarrow 4α + 4β = 4 \\[1em] \Rightarrow 4(α + β) = 4 \\[1em] \Rightarrow α + β = 1.\end{aligned}$$

Hence, proved that α + β = 1.

13Chapter Test

Prove that the points (3, 0), (6, 4) and (-1, 3) are the vertices of a right angled isosceles triangle.

Show SolutionHide Solution↓

Let the points be A(3, 0), B(6, 4) and C(-1, 3).

Prove that the points (3, 0), (6, 4) and (-1, 3) are the vertices of a right angled isosceles triangle. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(6 - 3)^2 + (4 - 0)^2} \\[1em] = \sqrt{3^2 + 4^2} \\[1em] = \sqrt{9 + 16} \\[1em] = \sqrt{25} \\[1em] = 5 \text{ units}. \\[1em] \therefore BC = \sqrt{(-1 - 6)^2 + (3 - 4)^2} \\[1em] = \sqrt{(-7)^2 + (-1)^2} \\[1em] = \sqrt{49 + 1} \\[1em] = \sqrt{50} \\[1em] = 5\sqrt{2}.\\[1em] \therefore AC = \sqrt{(-1 - 3)^2 + (3 - 0)^2} \\[1em] = \sqrt{(-4)^2 + 3^2} \\[1em] = \sqrt{16 + 9} \\[1em] = \sqrt{25} \\[1em] = 5.\end{aligned}$$

∴ AB = AC = 5

∴ ΔABC is an isosceles triangle

AB2 + AC2 = 52 + 52

= 25 + 25

= 50.

BC2 = $(5\sqrt{2})^2$ = 50.

Since, AB2 + AC2 = BC2.

Hence, proved that (3, 0), (6, 4) and (-1, 3) are the vertices of a right angled isosceles triangle.

14(i)Chapter Test

Show that the points (2, 1), (0, 3), (-2, 1) and (0, -1), taken in order, are the vertices of a square. Also find the area of the square.

Show SolutionHide Solution↓

Let A(2, 1), B(0, 3), C(-2, 1) and D(0, -1) be the four points.

Show that the points (2, 1), (0, 3), (-2, 1) and (0, -1), taken in order, are the vertices of a square. Also find the area of the square. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(0 - 2)^2 + (3 - 1)^2} \\[1em] = \sqrt{(-2)^2 + (2)^2} \\[1em] = \sqrt{4 + 4} \\[1em] = \sqrt{8} \text{ units}. \\[1em] \therefore BC = \sqrt{(-2 - 0)^2 + (1 - 3)^2} \\[1em] = \sqrt{(-2)^2 + (-2)^2} \\[1em] = \sqrt{4 + 4} \\[1em] = \sqrt{8} \text{ units}.\\[1em] \therefore CD = \sqrt{[0 - (-2)]^2 + [-1 - 1]^2} \\[1em] = \sqrt{[0 + 2]^2 + [-2]^2} \\[1em] = \sqrt{4 + 4} \\[1em] = \sqrt{8} \text{ units}. \\[1em] \therefore AD = \sqrt{(0 - 2)^2 + (-1 - 1)^2} \\[1em] = \sqrt{(-2)^2 + (-2)^2} \\[1em] =\sqrt{4 + 4} \\[1em] = \sqrt{8} \text{ units}.\end{aligned}$$

Since, AB = BC = CD = AD i.e. all sides are equal so, ABCD can be a rhombus or a square.

Calculating diagonals,

$$\begin{aligned}AC = \sqrt{(-2 - 2)^2 + (1 - 1)^2} \\[1em] =\sqrt{(-4)^2 + 0^2} \\[1em] = \sqrt{16} \\[1em] = 4 \text{ units}. \\[1em] BD = \sqrt{(0 - 0)^2 + (-1 - 3)^2} \\[1em] = \sqrt{0^2 + (-4)^2} \\[1em] = \sqrt{16} \\[1em] = \sqrt{4} \text{ units}.\end{aligned}$$

Since, diagonals are equal.

∴ ABCD is a square.

Area of square = (side)2

= (AB)2

= $(\sqrt{8})^2$

= 8 sq. units.

Hence, proved that (2, 1), (0, 3), (-2, 1) and (0, -1), taken in order, are the vertices of a square and area = 8 sq. units.

14(ii)Chapter Test

Show that the points (-3, 2), (-5, -5), (2, -3) and (4, 4), taken in order, are the vertices of rhombus. Also, find its area. Do the given points form a square?

Show SolutionHide Solution↓

Let A(-3, 2), B(-5, -5), C(2, -3) and D(4, 4).

Show that the points (-3, 2), (-5, -5), (2, -3) and (4, 4), taken in order, are the vertices of rhombus. Also, find its area. Do the given points form a square? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{[-5 - (-3)]^2 + [-5 - 2]^2} \\[1em] = \sqrt{[-5 + 3]^2 + [-7]^2} \\[1em] = \sqrt{[-2]^2 + [-7]^2} \\[1em] = \sqrt{4 + 49} \\[1em] = \sqrt{53}. \\[1em] \therefore BC = \sqrt{[2 - (-5)]^2 + [-3 - (-5)]^2} \\[1em] = \sqrt{[2 + 5]^2 + [-3 + 5]^2} \\[1em] = \sqrt{7^2 + 2^2} \\[1em] = \sqrt{49 + 4} \\[1em] = \sqrt{53}. \\[1em] \therefore CD = \sqrt{(4 - 2)^2 + [4 - (-3)]^2} \\[1em] = \sqrt{2^2 + 7^2} \\[1em] = \sqrt{4 + 49} \\[1em] = \sqrt{53}. \\[1em] \therefore AD = \sqrt{[4 - (-3)]^2 + (4 - 2)^2} \\[1em] = \sqrt{7^2 + 2^2} \\[1em] = \sqrt{49 + 4} \\[1em] = \sqrt{53}.\end{aligned}$$

Calculating diagonals,

$$\begin{aligned}AC = \sqrt{[2 - (-3)]^2 + [-3 - 2]^2} \\[1em] = \sqrt{[2 + 3]^2 + [-5]^2} \\[1em] = \sqrt{5^2 + [-5]^2} \\[1em] = \sqrt{25 + 25} \\[1em] = \sqrt{50} \\[1em] = 5\sqrt{2} \text{ units}. \\[1em] BD = \sqrt{[4 - (-5)]^2 + [4 - (-5)]^2} \\[1em] = \sqrt{[4 + 5]^2 + [4 + 5]^2} \\[1em] = \sqrt{9^2 + 9^2} \\[1em] = \sqrt{81 + 81} \\[1em] = \sqrt{162} \\[1em] = 9\sqrt{2} \text{ units}.\end{aligned}$$

Since, all sides are equal and diagonals are not equal.

∴ ABCD is a rhombus.

Area of rhombus = $\frac{1}{2} \times d_1 \times d_2$

$$\begin{aligned}= \frac{1}{2} \times 5\sqrt{2} \times 9\sqrt{2} \\[1em] = \frac{1}{2} \times 45 \times 2 \\[1em] = 45 \text{ sq. units}.\end{aligned}$$

Hence, ABCD is a rhombus and area = 45 sq. units.

15Chapter Test

The ends of a diagonal of a square have co-ordinates (-2, p) and (p, 2). Find p if the area of the square is 40 sq. units.

Show SolutionHide Solution↓

Given,

Ends of a diagonal of a square are (-2, p) and (p, 2).

Area of square = 40 sq. units

The ends of a diagonal of a square have co-ordinates (-2, p) and (p, 2). Find p if the area of the square is 40 sq. units. Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By formula,

Area of square = (side)2

∴ (side)2 = 40

⇒ side = $\sqrt{40} = 2\sqrt{10}$ units.

By formula,

Diagonal of a square = $\sqrt{2}$ × side = $\sqrt{2} \times 2\sqrt{10} = 2\sqrt{20}$.

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \Rightarrow 2\sqrt{20} = \sqrt{[p - (-2)]^2 + [2 - p]^2} \\[1em] \Rightarrow 2\sqrt{20} =\sqrt{[p + 2]^2 + [2 - p]^2} \\[1em] \Rightarrow 2\sqrt{20} = \sqrt{p^2 + 4 + 4p + 4 + p^2 - 4p} \\[1em] \Rightarrow 2\sqrt{20} = \sqrt{2p^2 + 8}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow 4 \times 20 = 2p^2 + 8 \\[1em] \Rightarrow 2p^2 = 80 - 8 \\[1em] \Rightarrow 2p^2 = 72 \\[1em] \Rightarrow p^2 = \frac{72}{2} \\[1em] \Rightarrow p^2 = 36 \\[1em] \Rightarrow p = \sqrt{36} \\[1em] \Rightarrow p = \pm 6.\end{aligned}$$

Hence, p = ±6.

16Chapter Test

What type of quadrilateral do the points A(2, -2), B(7, 3), C(11, -1) and D(6, -6), taken in that order, form?

Show SolutionHide Solution↓
What type of quadrilateral do the points A(2, -2), B(7, 3), C(11, -1) and D(6, -6), taken in that order, form? Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

$$\begin{aligned}d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \\[1em] \therefore AB = \sqrt{(7 - 2)^2 + [3 - (-2)]^2} \\[1em] = \sqrt{5^2 + 5^2} \\[1em] = \sqrt{25 + 25} \\[1em] = \sqrt{50}. \\[1em] \therefore BC = \sqrt{(11 - 7)^2 + (-1 - 3)^2} \\[1em] = \sqrt{4^2 + (-4)^2} \\[1em] = \sqrt{16 + 16} \\[1em] = \sqrt{32}. \\[1em] \therefore CD = \sqrt{(6 - 11)^2 + [-6 - (-1)]^2} \\[1em] = \sqrt{(-5)^2 + (-5)^2} \\[1em] = \sqrt{25 + 25} \\[1em] = \sqrt{50}. \\[1em] \therefore AD = \sqrt{(6 - 2)^2 + [-6 - (-2)]^2} \\[1em] = \sqrt{4^2 + (-4)^2} \\[1em] = \sqrt{16 + 16} \\[1em] = \sqrt{32}.\end{aligned}$$

Hence,

AB = CD and BC = AD

Since, opposite sides are equal,

Hence, proved that ABCD is a rectangle.

17Chapter Test

Find the coordinates of the centre of the circle passing through the three given points A(5, 1), B(-3, -7) and C(7, -1).

Show SolutionHide Solution↓

Let O(x, y) be the coordinates of the centre of the circle. Points A(5, 1), B(-3, -7), and C(7, -1) are on the circle.

Find the coordinates of the centre of the circle passing through the three given points A(5, 1), B(-3, -7) and C(7, -1). Coordinate Geometry, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

By distance formula,

d = $\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

As, OA = OB [∵ Both are radius of the same circle]

$$\begin{aligned}\therefore \sqrt{(x - 5)^2 + (y - 1)^2} = \sqrt{[x - (-3)]^2 + [y - (-7)]^2} \\[1em] \Rightarrow \sqrt{x^2 + 25 - 10x + y^2 + 1 - 2y} = \sqrt{[x + 3]^2 + [y + 7]^2} \\[1em] \Rightarrow \sqrt{x^2 + y^2 - 10x - 2y + 26} = \sqrt{x^2 + 9 + 6x + y^2 + 49 + 14y} \\[1em] \Rightarrow \sqrt{x^2 + y^2 - 10x - 2y + 26} = \sqrt{x^2 + y^2 + 6x + 14y + 58}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow x^2 + y^2 - 10x - 2y + 26 = x^2 + y^2 + 6x + 14y + 58 \\[1em] \Rightarrow x^2 - x^2 + y^2 - y^2 + 6x + 10x + 14y + 2y = 26 - 58 \\[1em] \Rightarrow 16x + 16y = -32 \\[1em] \Rightarrow 16(x + y) = -32 \\[1em] \Rightarrow x + y = \frac{-32}{16} \\[1em] \Rightarrow x + y = -2 \\[1em] \Rightarrow x = -2 - y \space .........(1).\end{aligned}$$

As, OC = OB [∵ Both are radius of the same circle]

$$\begin{aligned}\therefore \sqrt{(x - 7)^2 + [y - (-1)]^2} = \sqrt{[x - (-3)]^2 + [y - (-7)]^2} \\[1em] \Rightarrow \sqrt{x^2 + 49 - 14x + [y + 1]^2} = \sqrt{[x + 3]^2 + [y + 7]^2} \\[1em] \Rightarrow \sqrt{x^2 + 49 - 14x + y^2 + 1 + 2y} = \sqrt{x^2 + 9 + 6x + y^2 + 49 + 14y} \\[1em] \Rightarrow \sqrt{x^2 + y^2 - 14x + 2y + 50} = \sqrt{x^2 + y^2 + 6x + 14y + 58}\end{aligned}$$

On squaring both sides,

$$\begin{aligned}\Rightarrow x^2 + y^2 - 14x + 2y + 50 = x^2 + y^2 + 6x + 14y + 58 \\[1em] \Rightarrow x^2 + y^2 - x^2 - y^2 + 6x + 14x + 14y - 2y = 50 - 58 \\[1em] \Rightarrow 20x + 12y = -8 \\[1em] \Rightarrow 5x + 3y = -2 \\[1em]\end{aligned}$$

Substituting value of x in above equation from equation 1 :

⇒ 5(-2 - y) + 3y = -2

⇒ -10 - 5y + 3y = -2

⇒ -2y = -2 + 10

⇒ -2y = 8

⇒ y = -4.

⇒ x = -2 - y = -2 - (-4) = -2 + 4 = 2.

C = (x, y) = (2, -4).

Hence, the coordinates of the centre of the circle are (2, -4).

Press ↓ to reveal a solution and move to the next question. Back to ML Aggarwal Solutions Understanding ICSE Mathematics Class 9.