If $f(x)=\sin ^{-1}\left(\frac{2 x}{1+x^2}\right)+\cos ^{-1}\left(\frac{1-x^2}{1+x^2}\right), x \in(1,…

If $f(x)=\sin ^{-1}\left(\frac{2 x}{1+x^2}\right)+\cos ^{-1}\left(\frac{1-x^2}{1+x^2}\right), x \in(1, \infty)$, then $f^{\prime}(x)$
  1. $\frac{-4}{1+x^2}$
  2. 0
  3. $\frac{2 x}{1-x^2}$
  4. $\frac{4}{1+x^2}$

Solution

$\begin{aligned} & f(x)=\sin ^{-1}\left(\frac{2 x}{1+x^2}\right)+\cos ^{-1}\left(\frac{1-x^2}{1+x^2}\right) \\ & \Rightarrow f(x)=\sin ^{-1}\left(\frac{2 \tan \theta}{1+\tan ^2 \theta}\right)+\cos ^{-1}\left(\frac{1-\tan ^2 \theta}{1+\tan ^2 \theta}\right) \\ & \Rightarrow f(x)=\sin ^{-1}(\sin 2 \theta)+\cos ^{-1}(\cos 2 \theta) \\ & \Rightarrow f(x)=\pi-2 \theta+2 \theta=\pi \\ & \Rightarrow f^{\prime}(x)=0\end{aligned}$

Asked in: MHT CET 2022 (08 Aug Shift 2)

Practice more Differentiation questions on Aicharya