$\int \frac{10^{\frac{x}{2}}}{10^{-x}-10^x} d x=$

$\int \frac{10^{\frac{x}{2}}}{10^{-x}-10^x} d x=$
  1. $2 \sqrt{10^{-x}-10^x+c}$
  2. $\frac{1}{\log 10} \sin ^{-1}\left(10^x\right)+c$
  3. $2 \sqrt{10^{-x}+10^x+c}$
  4. $\frac{1}{\log 10} \cos ^{-1}\left(10^x\right)+c$

Solution

Let $I=\int \frac{10^{\frac{x}{2}}}{10^{-x}-10^x} d x$ $\begin{aligned} & =\int \frac{10^{\frac{x}{2}}}{\sqrt{\frac{1}{10^x}-10^x}} d x=\int \frac{10^{\frac{x}{2}}}{\sqrt{\frac{1-\left(10^x\right)^2}{10^x}}} d x \\ & =\int \frac{10^{\frac{x}{2}} \cdot 10^{\frac{x}{2}}}{\sqrt{1-\left(10^x\right)^2}} d x=\int \frac{10^x}{\sqrt{1-\left(10^x\right)^2}} d x \end{aligned}$ Put $10^{\mathrm{x}}=\mathrm{t} \Rightarrow 10^{\mathrm{x}}(\log 10) \mathrm{dx}=\mathrm{dt}$ $\therefore \mathrm{I}=\frac{1}{\log 10} \int \frac{\mathrm{dt}}{\sqrt{1-\mathrm{t}^2}}=\frac{1}{\log 10} \sin ^{-1}(\mathrm{t})+\mathrm{c}=\frac{1}{\log 10} \sin ^{-1}\left(10^{\mathrm{x}}\right)+\mathrm{c}$

Asked in: MHT CET 2021 (23 Sep Shift 2)

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