If the area enclosed between the curves y = k x 2 and x = k y 2 ,   k > 0 , is 1   s q . &#160…

If the area enclosed between the curves y=kx2 and x=ky2, k>0, is 1 sq. unit. Then k is
  1. 3
  2. 13
  3. 32
  4. 23

Solution

The given curves are, y=kx2, x=ky2

To find the point of intersection of the curves, put y from the first curve into second, to get

x=kk2x4

x=0 or x3=1k3x=1k

Hence, y=0 or y=k1k2=1k

Therefore, point of intersection is 1k, 1k.



Hence, the required area is 01ky2-y1dx=1

01kxk-kx2dx=1

1kx3/23/2-kx3301k=1

23k2-13k2=1

k2=13

k=±13

But, given k>0

So, k=13.

Asked in: JEE Main 2019 (10 Jan Shift 1)

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