$\int \frac{e^{\frac{x}{2}}}{\sqrt{e^{-x}-e^x}} \mathrm{~d} x=\sin ^{-1}(f(x))+C, \quad$ (where $\quad C…

$\int \frac{e^{\frac{x}{2}}}{\sqrt{e^{-x}-e^x}} \mathrm{~d} x=\sin ^{-1}(f(x))+C, \quad$ (where $\quad C \quad$ is constant of integration.) then $f(2)$ has the value
  1. $e$
  2. $e^2$
  3. $e^{\frac{1}{2}}$
  4. $e^{\frac{3}{2}}$

Solution

$\begin{aligned} & \int \frac{e^{x / 2}}{\sqrt{e^{-x}-e^x}} \mathrm{~d} x=\int \frac{e^x \mathrm{~d} x}{\sqrt{1-\left(e^x\right)^2}}\left[\text { Multiplying } N^r \text { and } D^r \text { by } e^{\frac{x}{2}} \text { ] }\right. \\ & =\int \frac{\mathrm{d} t}{\sqrt{1-t^2}}=\sin ^{-1} t+C=\sin ^{-1}\left(e^x\right)+C\left[\text { let } e^x=t\right] \\ & \Rightarrow f(x)=e^x \\ & \Rightarrow f(2)=e^2\end{aligned}$

Asked in: MHT CET 2022 (11 Aug Shift 1)

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