$\int \frac{\tan ^4 \sqrt{x} \cdot \sec ^2 \sqrt{x}}{\sqrt{x}} d x=$

$\int \frac{\tan ^4 \sqrt{x} \cdot \sec ^2 \sqrt{x}}{\sqrt{x}} d x=$
  1. $\frac{-5}{2}[\tan \sqrt{x}]^5+c$
  2. $[\tan \sqrt{\mathrm{x}}]^5+\mathrm{c}$
  3. $\frac{2}{5}[\tan \sqrt{x}]^5+c$
  4. $\frac{5}{2}[\tan \sqrt{x}]^5+c$

Solution

$\begin{aligned} & \text { Let } I=\int \frac{\tan ^4 \sqrt{x} \cdot \sec ^2 \sqrt{x}}{\sqrt{x}} d x \\ & \text { Put } \sqrt{x}=t \Rightarrow \frac{1}{2 \sqrt{x}} d x=d t \\ & \therefore I=2 \int \tan ^4 \operatorname{tsec}^2 t d t \end{aligned}$ Put $\tan \mathrm{t}=\mathrm{u} \quad \Rightarrow \sec ^2 \mathrm{tdt}=\mathrm{du}$ $\begin{aligned} & \therefore \mathrm{I}=2 \int \mathrm{u}^4 \mathrm{du} \\ & =\frac{2 \mathrm{u}^5}{5}=\frac{2(\tan \mathrm{t})^5}{5}=\frac{2}{5} \tan ^5 \sqrt{\mathrm{x}}+\mathrm{c} \end{aligned}$

Asked in: MHT CET 2021 (22 Sep Shift 2)

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