Chapter 7 Coordinate Geometry Important Questions for CBSE Class 10 Maths Board Exams
Important Questions for Chapter 7 Coordinate Geometry Class 10 Maths
Coordinate Geometry Class 10 Maths Important Questions Very Short Answer (1 Mark)
A(0, 5) and B(-3, 1).
Distance between A and B,
Solution
Since it is equidistant from the points A(-2, 0) and B(6, 0) then
AP = BP
⇒ AP2 = BP2
Using distance formula we have,
[x-(2)]2 + (0-0)2 = (x+6)2 + (0-0)2
⇒ (x+2)2 = (x+6)2
⇒ x2 + 4x + x = x2 + 12x + 36
⇒ 8x = -32
⇒ x = -4
Hence, required point P is (-4, 0).
3. Find the distance of a point P(x,y) from the origin.
Solution
Distance between origin (0, 0) and point P(x,y) is
Solution
When the points are collinear,
x1(y2 – y3) + x2(y3 – y1) + x3(y1 – y2) = 0
⇒ x(-4 – (-5)) + (-3)(-5 – 2) + 7(2 – (-4)) = 0
⇒ x(1) + 21 + 42 = 0
⇒ x + 63 = 0
∴ x = -63
7. For what value of k will k + 9, 2k – 1 and 2k + 7 are the consecutive terms of an A.P.?
Solution
As we know, a2 – a1 = a3 – a2
2k – 1 – (k + 9) = 2k + 7 – (2k – 1)
⇒ 2k – 1 – k – 9 = 2k + 7 – 2k + 1
⇒ k – 10 = 8
∴ k = 8 + 10 = 18
8. ABCD is a rectangle whose three vertices are B(4, 0), C(4, 3) and D(0, 3). Calculate the length of one of its diagonals.
Solution
AB = 4 units
BC = 3 units
AC2 = AB2 + BC2 …(Pythagoras’ theorem)
= (4)2 + (3)2
= 16 + 9 = 25
∴ AC = 5 cm
Coordinate Geometry Class 10 Maths Important Questions Short Answer-I (2 Marks)
Solution
Let the point P be (2y, y). Since PQ = PR, we have
Squaring both sides,
(2y-2)2 + (y+5)2 = (2y+3)2 + (y-6)2
⇒ -8y + 4 + 10y + 25 = 12y + 9 -12y + 36
⇒ 2y + 29 = 45
⇒ y = 8
Hence, the coordinates of point P are (16,8).
Solution
When points are collinear,
∴ Area of ∆ABC = 0
= (x1 (y2 – y3) + x2(y3 – y1) + x3(y1 – y2)) = 0
= x (7 – 5) – 5 (5 – y) -4 (y – 7) = 0
= 2x – 25 + 5y – 4y + 28 = 0
∴ 2x + y + 3 = 0 is the required relation.
13. Find a relation between x and y such that the point P(x, y) is equidistant from the points A (2, 5) and B (-3, 7).
Solution
Let P (x, y) be equidistant from the points A (2, 5) and B (-3, 7).
∴ AP = BP …(Given)
AP2 = BP2 …(Squaring both sides)
(x – 2)2 + (y – 5)2 = (x + 3)2 + (y – 7)2
⇒ x2 – 4x + 4 + y2 – 10y + 25
⇒ x2 + 6x + 9 + y2 – 14y + 49
⇒ -4x – 10y – 6x + 14y = 9 +49 – 4 – 25
⇒ -10x + 4y = 29
∴ 10x + 29 = 4y is the required relation.
14. The points A(4,7), B(p,3) and C (7,3) are the vertices of a right triangle, right-angled at B. Find the value of p.
Solution
As per question, triangle is shown below. Here ABC is a right angle triangle,
AB2 + BC2 = AC2
(p-4)2 + (3-7)2 + (7-p)2 + (3-3)2 = (7-4)2 + (3-4)2
⇒ (p-4)2 + (-4)2 + (7-p)2 + 0 = 32 + (-4)2
⇒ p2 - 8p + 16 + 16 + 49 + p2 - 14p = 9 + 16
⇒ 2p2 - 22p + 81 = 25
⇒ 2p2 - 22p + 56 = 0
⇒ p2 - 11p + 28 = 0
⇒ (p-4) (p-7) = 0
⇒ p = 7 or 4
15. If A(4,3), B(-1,y) and C(3,4) are the vertices of a right triangle , ABC right angled at A, then find the value of y.
Solution
As per question, triangle is shown below.
Now,
AB2 + AC2 = BC2
(4+1)2 + (3-y)2 + (4-3)2 = (3+1)2 + (4-y)2
⇒ 52 + (3-y)2 + (-1)2 + 12 = 42 + (4-y)2
⇒ 25 + 9 - 6y + y2 + 1 + 1 = 16 + 16 - 8y + y2
⇒ 36 + 2y - 32 = 0
⇒ 2y + 4 = 0
⇒ y = -2
16. Show that the points (a,a), (-a, -a) and (-√3a, √3a) are the vertices of an equilateral triangle.
Solution
Let A(a,a), B(-a, -a) and C(√3a, √3a)
Since AB = BC = AC, therefore ABC is an equilateral triangle.
17. If A(4, 3), B(-1, y) and C(3, 4) are the vertices of a right triangle ABC, right-angled at A, then find the value of y.
Solution
We have A(4, 3), B(-1, y) and C(3, 4). In right angled triangle ABC,
(BC)2 = (AB)2 + (AC) …(Pythagoras theorem)
⇒ (-1 – 3)2 + (y – 4)2 = (4 + 1)2 + (3 – y)2 + (4 – 3)2 + (3 – 4)2 …(using distance formula)
⇒ (-4)2 + (y2 – 8y + 16)
⇒ (5)2 + (9 – 6y + y2) + (1)2 + (-1)2
⇒ y2 – 8y + 32 = y2 – 6y + 36 = 0
⇒ -8y + 6y + 32 – 36
⇒ -2y – 4 = 0
⇒ -2y = 4
∴ y = -2
18. If the mid-point of the line segment joining A(x/2, y+1/2) and B(x+1, y-3) is C(5, -2), find x,y.
Solution
If the mid-point of the line segment joining A(x/2, y+1/2) and B(x+1, y-3) is C(5, -2) then at mid point,
⇒ y + 1 + 2y - 6 = -8
⇒ y = -1
19. Show that A(6,4) B(5,-2) and C(7,-2) are the vertices of an isosceles triangle.
Solution
We have A(6,4) B(5,-2) and C(7,-2).
Since two sides of a triangle are equal in length, triangle is an isosceles triangle.
20. If the line segment joining the points A(2,1) and B(5,-8) is trisected at the points P and Q, find the coordinates P.
Solution
As per question, line diagram is shown below.
Let P(x, y) divides AB in the ratio 1:2.
Using section formula we get,
Hence, coordinates of P are (3,-2).
21. Three vertices of a parallelogram taken in order are (-1, 0), (3, 1) and (2, 2) respectively. Find the coordinates of fourth vertex. (2011D)
Solution
Let A(-1, 0), B(3, 1), C(2, 2) and D(x, y) be the vertices of a parallelogram ABCD taken in order. Since, the diagonals of a parallelogram bisect each other.
∴ Coordinates of the mid-point of AC = Coordinates of the mid-point of BD
Hence, coordinates of the fourth vertex, D(-2, 1).
22. If two adjacent vertices of a parallelogram are (3,2) and (-1,0) and the diagonals intersect at (2,-5) then find the co-ordinates of the other two vertices.
Solution
Let two other co-ordinates be (x,y) and (x',y') respectively using mid-point formula.
As per question parallelogram is shown below.
Hence, coordinates of C(1,-12) and D(5,-10).
23. If A(5, 2), B(2, -2) and C(-2, t) are the vertices of a right angled triangle with ∠B = 90°, then find the value of t. (2015D)
Solution
ABC is a right angled triangle,
∴ AC2 = BC2 + AB2 …(i) …(Pythagoras theorem)
Using distance formula,
AB2 = (5 – 2)2 + (2 + 2)
= 25
BC2 = (2 + 2)2 + (t + 2)2
= 16 + (t + 2)2
AC2 = (5 + 2)2 + (2 – t)2
= 49 + (2 – t)2
Putting values of AB2, AC2 and BC2 in equation (i), we get
49 + (2 – t)2 = 16 + (t + 2)2 + 25
∴ 49 + (2 – t)2 = 41 + (t + 2)2
⇒ (t + 2)2 – (2 – t)2 = 8
⇒ (t2 + 4 + 4t – 4 – t2 + 4t) = 8
8t = 8
⇒ t = 1
24. 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.
Solution
We have,
P(2,-1), Q(3,4), R(-2,3) and S(-3,-2)
Since, all the four sides are equal, PQRS is a rhombus.
Since, PQR is not a right triangle, PQRS is a rhombus but not a square.
Coordinate Geometry Class 10 Maths Important Questions Short Answer-II (3 Marks)
25. Find the ratio in which the segment joining the points (1,-3) and (4,5) is divided by x-axis? Also find the coordinates of this point on x-axis.
Solution
Let the required ratio be k:1 and the point on x-axis be (x,0).
Here,
(x1, y1) = (1, -3)
and (x2, y2) = (4,5)
Using section formula y coordinate we obtain,
Hence, the required ratio is 3/5 i.e. 3:5.
Now, again using section formula for x, we obtain
Coordinate of P is (117/8, 0).
26. If the point C(-1, 2) divides internally the line segment joining A(2,5) and B(x, y) in the ratio 3 : 4 find the coordinates of B.
Solution
From the given information we have drawn the figure as below.
3y + 20 = 14
⇒ 3y = 14 - 20 = -6
⇒ y = -2
Hence, the coordinates of B(x, y) is (-5,-2).
27. If the co-ordinates of points A and B are (-2, -2) and (2, -4) respectively, find the co-ordinates of P such that AP = 3/7 AB, where P lies on the line segment AB.
Solution
We have,
AP = 3/7 AB
⇒ AP:PB = 3:4
As per question, line diagram is shown below.
Solution
PQ = 10 …(Given)
⇒ PQ2 = 102 = 100 …(Squaring both sides)
(9 – x)2 + (10 – 4)2 = 100 …(using distance formula)
⇒ (9 – x)2 + 36 = 100
⇒ (9 – x)2 = 100 – 36 = 64
⇒ (9 – x) = ± 8 …(Taking square-root on both sides)
⇒ 9 – x = 8 or 9 – x = -8
⇒ 9 – 8 = x or 9+ 8 = x
⇒ x = 1 or x = 17
29. Find the value of y for which the distance between the points A (3,-1) and B (11, y) is 10 units.
Solution
AB = 10 units …(Given)
⇒ AB2 = 102 = 100 …(Squaring both sides)
(11 – 3)2 + (y + 1)2 = 100
⇒ 82 + (y + 1)2 = 100
⇒ (y + 1)2 = 100 – 64 = 36
⇒ y + 1 = ±6 …(Taking square-root on both sides)
⇒ y = -1 ± 6
∴ y = -7 or 5
30. The co-ordinates of the vertices of △ABC are A(7, 2), B(9, 10) and C(1, 4). If E and F are the mid-points of AB and AC respectively, prove that EF = 1/2 BC.
Solution
Let the mid-points of AB and AC be E(x1, y1) and F(x2, y2). As per question, triangle is shown below.
Solution
Let the two points (15, 5) and (9, 20) are divided in
the ratio : k 1 by point P(11,15).
Using Section formula, we get
⇒ 11 + 11k = 15 + 9k
⇒ k = 2
Thus ratio is 2 : 1.
32. Find the point on y-axis which is equidistant from the points (5, -2) and (-3, 2).
Solution
Let the point be (0,y).
52 + (y+2)2 = 32 + (y-2)2
or, y2 + 25 + 4y + 4 = 9 - 4y + 4
8y = -16 or, y = -2
or, Point (0, -2)
33. The vertices of △ABC are A(6, -2), B(0, -6) and C(4,8). Find the co-ordinates of mid-points of AB, BC and AC.
Solution
Let mid-point of AB, BC and AC be D(x1, y1), E(x2, y2) and F(x3, y3). As per question, triangle is shown below.
Using section formula, the co-ordinates of the points D, E, F are:
The co-ordinates of the mid-points of AB, BC and AC are D(3, -4), E(2,1) and F(5,3) respectively.
Solution
PA = QA …(Given)
⇒ PA2 = QA2 …(Squaring both sides)
(3 – 6)2 + (y – 5)2 = (3 – 0)2 + (y + 3)2
⇒ 9 + (y – 5)2 = 9 + (y + 3)2
⇒ (y – 5)2 = (y + 3)2
⇒ y – 5 = ±(y + 3) …(Taking square root of both sides)
⇒ y – 5 = y + 3 y – 5 = -y – 3
0 = 8 …(not possible)
∴ y = 1
35. If the point P(x, y) is equidistant from the points A(a + b, b – a) and B(a – b, a + b), prove that bx = ay.
Solution
PA = PB …(Given)
PA2 = PB2 …(Squaring both sides)
⇒ [(a+b) – x]2 + [(b-a) – y)2 = [(a–b) – x]2 + [(a+b) – y]2
⇒ (a+b)2 + x2 – 2(a+b)x + (b–a)2 + y2 – 2(b–a)y = (a–b)2 + x2 – 2(a–b)x + (a+b)2 + y2 – 2(a+b)y …[∵ (a–b) 2 = (b–a)2]
⇒ -2(a + b)x + 2(a – b)x = -2(a + b)y + 2(b – a)y
⇒ 2x(-a – b + a – b) = 2y(-a – b + b – a)
⇒ -2bx = –2ay
⇒ bx = ay
36. If the point P(k – 1, 2) is equidistant from the points A(3, k) and B(k, 5), find the values of k.
Solution
PA = PB …(Given)
PA2 = PB2 …(Squaring both sides)
⇒ (k – 1 – 3)2 + (2 – k)2 = (k – 1 – k)2 + (2 – 5)2
⇒ (k – 4)2 + (2 – k)2 = (-1)2 + (-3)2
⇒ k2 – 8k + 16 + 4 + k2 – 4k = 1 + 9
⇒ 2k2 – 12k + 20 – 10 = 0
⇒ 2k2 – 12k + 10 = 0 …(Dividing by 2)
⇒ k2 – 6k + 5 = 0
⇒ k2 – 5k – k + 5 = 0
⇒ k(k – 5) – 1(k – 5) = 0
⇒ (k – 5) (k – 1) = 0
⇒ k – 5 = 0 or k – 1 = 0
∴ k = 5 or k = 1
37. Find the area of the rhombus of vertices (3,0), (4,5), (-1,4) and (-2,-1) taken in order.
Solution
We have,
A(3,0), B(4,5), C(-1,4) and D(-2,-1)