Maharashtra BoardEnglish MediumSTD 12 ScienceMathsIndefinite Integration3 Marks
Question
Evaluate the following functions : $\int \frac{e^x+1}{e^x-1} \cdot d x$
✓
Answer
$ \begin{aligned} & I=\int \frac{e^x-1+2}{e^x-1} \cdot d x \\ & =\int\left(\frac{e^x-1}{e^x-1}+\frac{2}{e^x-1}\right) \cdot d x \\ & =\int\left(1+\frac{2}{e^x-1}\right) \cdot d x \\ & =\int d x+\int \frac{2}{e^x\left(1-e^{-x}\right)} \cdot d x \\ & =\int 1 d x+2 \int \frac{e^{-x}}{1-e^{-x}} \cdot d x \\ & \text { put }\left(1-e^{-x}\right)=t \\ & \text { Differentiate w.r.t. } x \\ & -\left(e^{-x}\right)(-1) \cdot d x=1 d t \\ & e^{-x} \cdot d x=1 d t \\ & \mathrm{I}=\int 1 d x+2 \int \frac{1}{t} \cdot d t \\ & =x+2 \cdot \log (t)+c \\ & =x+2 \log \left(1-e^{-x}\right)+c \\ & \therefore \quad \int \frac{e^x+1}{e^x-1} \cdot d x=x+2 \log \left(1-e^{-x}\right)+c \\ \end{aligned} $
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