If the area of the region enclosed by the curve $x^2+y^2=16$ and then lines $x=2$ and $x=3$ is $\left(3…

If the area of the region enclosed by the curve $x^2+y^2=16$ and then lines $x=2$ and $x=3$ is $\left(3 \sqrt{7}-4 \sqrt{3}-\frac{8 \pi}{3}+k\right)$ sq units, then $k$ equals
  1. $16 \sin ^{-1}\left(\frac{3}{4}\right)$
  2. $8 \sin ^{-1}\left(\frac{3}{4}\right)$
  3. $4 \sin ^{-1}\left(\frac{3}{4}\right)$
  4. $2 \sin ^{-1}\left(\frac{3}{4}\right)$

Solution

Area of region enclosed by the curve $x^2+y^2=16$ and line $x=2$ and $x=3$ is $ \begin{aligned} & A=\int_2^3 \sqrt{16-x^2} d x \\ & A=\left[\frac{x}{2} \sqrt{16-x^2}+8 \sin ^{-1} \frac{x}{4}\right]_2^3 \\ & \Rightarrow 3 \sqrt{7}-4 \sqrt{3}-\frac{8 \pi}{3}+k \\ & =\left(\frac{3}{2} \sqrt{7}+8 \sin ^{-1} \frac{3}{4}\right)-\left(2 \sqrt{3}+8 \sin ^{-1} \frac{2}{4}\right) \\ & \Rightarrow 3 \sqrt{7}-4 \sqrt{3}-\frac{8 \pi}{3}+k \\ & =\frac{3}{2} \sqrt{7}+8 \sin ^{-1} \frac{3}{4}-2 \sqrt{3}-\frac{8 \pi}{6} \\ & =\frac{1}{2}\left(3 \sqrt{7}+16 \sin ^{-1} \frac{3}{4}-4 \sqrt{3}-\frac{8 \pi}{3}\right) \\ & \therefore \quad k=16 \sin ^{-1}\left(\frac{3}{4}\right) \\ & \end{aligned} $

Asked in: AP EAMCET 2021 (25 Aug Shift 1)

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