The value of the integral $\int_0^1 \sqrt{\frac{1-x}{1+x}} d x$ is

The value of the integral $\int_0^1 \sqrt{\frac{1-x}{1+x}} d x$ is
  1. $\left(\frac{\pi}{2}\right)-1$
  2. $-1$
  3. $\left(\frac{\pi}{2}\right)+1$
  4. $1$

Solution

$\begin{aligned} & \int_0^1 \sqrt{\frac{1-x}{1+x}} d x=\int_0^1 \frac{1-x}{\sqrt{1-x^2}} d x=\int_0^1 \frac{d x}{\sqrt{1-x^2}}+\int_0^1 \frac{-2 x}{2 \sqrt{1-x^2}} d x \\ & =\left[\sin ^{-1} x\right]_0^1+\left[\sqrt{1-x^2}\right]_0^1 \\ & =\left\{\sin ^{-1}(1)-\sin ^{-1}(0)\right\}+\left\{\sqrt{1-1^2}-\sqrt{1-0^2}\right\} \\ & =\frac{\pi}{2}-0+0-1 \\ & =\frac{\pi}{2}-1\end{aligned}$

Asked in: MHT CET 2022 (06 Aug Shift 2)

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