JEE Advanced 2020 Paper 1 · Mathematics · Area Under Curves · hard
The area of the region \(x,y):x^2+y^2≤ 8, y^2≥ 2x\ is
Single correct option
The area of the region {(x,y):x2+y2≤8,y2≥2x} is
A.6π+34
B.2π+34
C.4π−34
D.6π−34
Show answer and solution
Answer:(D) 6π−34
The circle has area 8π. The parabola y2=2x meets the circle where x2+2x=8, i.e. at x=2, y=±2. The part of the disc lying inside the parabola (y2≤2x) is bounded by the parabola for 0≤x≤2 and by the circle for 2≤x≤22. Its area is 2[∫022xdx+∫2228−x2dx]. The first integral equals 8/3. The second equals [2x8−x2+4sin−122x]222=2π−(2+π)=π−2. So the inside part is 2(π+32)=2π+34, and the required area is 8π−2π−34=6π−34. A numerical integration agrees (≈17.516).