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NCERT Class XII Mathematics Chapter - - Solutions

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Choose the correct answers in Exercises 269 to 272.
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Question : 269 of 271
Marks: +1, -0
∫dxex+e−x\int \frac{dx}{e^x+e^{-x}} is equal to
Solution:  
I=∫dxex+e−xI=\int \frac{dx}{e^x+e^{-x}} =∫dxex+1ex=\int \frac{dx}{e^x+\frac{1}{e^x}}
⇒I=∫exdx(ex)2+1\Rightarrow I=\int \frac{e^x dx}{(e^x)^2+1}
Put ex=te^x = t ⇒exdx=dt\Rightarrow e^x dx = dt
∴I=∫dtt2+1\therefore I=\int \frac{dt}{t^2+1} =tan⁡−1t+C=\tan^{-1}t+C =tan⁡−1(ex)+C=\tan^{-1}(e^x)+C
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