$\text {If } y=\sin ^{-1}\left[\cos \sqrt{\frac{1+x}{2}}\right]+x^x \text {, then } \frac{d y}{d x} \text {…

$\text {If } y=\sin ^{-1}\left[\cos \sqrt{\frac{1+x}{2}}\right]+x^x \text {, then } \frac{d y}{d x} \text { at } x=1 \text { is }$
  1. $\frac{5}{4}$
  2. $\frac{-1}{4}$
  3. $\frac{3}{4}$
  4. $\frac{-5}{4}$

Solution

$\begin{aligned} & \sin ^{-1}\left[\cos \sqrt{\frac{1+x}{2}}\right]+x^x \\ & =\sin ^{-1}\left[\sin \left(\frac{\pi}{2}-\sqrt{\frac{1+x}{2}}\right)\right]+x^x \\ & =\frac{\pi}{2}-\sqrt{\frac{1+x}{2}+x^x} \\ & \therefore \frac{d y}{d x}=0-\frac{1}{\sqrt{2}} \cdot \frac{d}{d x}(\sqrt{1+x})+\frac{d}{d x}\left(x^x\right) \end{aligned}$ Let $\mathrm{u}=\mathrm{x}^{\mathrm{x}} \Rightarrow \log \mathrm{u}=\mathrm{x} \log \mathrm{x}$ $\begin{aligned} & \therefore \frac{1}{u} \frac{d u}{d x}=\frac{x}{x}+\log x \Rightarrow \frac{d y}{d x}=x^x(1+\log x) \\ & \therefore \frac{d y}{d x}=\frac{-1}{\sqrt{2}}\left[\frac{1}{2 \sqrt{1+x}}\right]+x^x(1+\log x) \\ & \therefore\left[\frac{d y}{d x}\right]_{x=1}=\left(\frac{-1}{\sqrt{2}}\right)\left(\frac{1}{2 \sqrt{2}}\right)+1=\frac{-1}{4}+1=\frac{3}{4} \end{aligned}$

Asked in: MHT CET 2021 (20 Sep Shift 2)

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