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Question : 25
Total: 29
Using integration find the area of the region bounded by the parabola y 2 = 4x and the circle 4 x 2 + 4 y 2 = 9.
Solution:
The respective equations for the parabola and the circle are:
y 2 = 4x ... (1)
4 x 2 + 4 y 2 = 9 ... (2)
orx 2 + y 2 = (
) 2
Equation (1) is a parabola with vertex (0, 0) which opens to the right and equation (2) is a circle with centre (0, 0) and radius
From equations (1) and (2), we get:
4 x 2 + 4 (4x) = 9
4 x 2 + 16x - 9 = 0
4 x 2 + 18x - 2x - 9 = 0
2x (2x + 9) - 1 (2x + 9) = 0
(2x + 9) (2x - 1) = 0
x = -
,
For x =−
, y 2 = 4 ( −
) , which is not possible, hence x =
Therefore, the given curves intersect at x =
Required area of the region bound by the two curves
= 2
2 √ x d x + 2
√
− x 2 d x
= 4|
x
| 0
+ 2 |
√
− x 2 +
s i n − 1 (
) s i n − 1 (
) |
=
(
)
+ 2 | 0 +
s i n − 1 −
√ 2 −
s i n − 1 (
) |
=
(
) +
(
) -
−
s i n − 1 (
)
=
+
-
−
s i n − 1 (
)
or
Equation (1) is a parabola with vertex (0, 0) which opens to the right and equation (2) is a circle with centre (0, 0) and radius
From equations (1) and (2), we get:
2x (2x + 9) - 1 (2x + 9) = 0
(2x + 9) (2x - 1) = 0
x = -
For x =
Therefore, the given curves intersect at x =
Required area of the region bound by the two curves
= 2
= 4
=
=
=
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