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Need solution for RD Sharma maths class 12 chapter Indefinite Integrals exercise 18.8 question 23

Answers (1)

Answer:

        -log\left | e^{-x}+1 \right |+C

Hint:

        \int \! \frac{1}{x}dx=log\left | x \right |+C

Given:

        \int \! \frac{1}{e^{x}+1}dx

Explanation:

        \int \! \frac{1}{e^{x}(1+\frac{1}{e^{x}})}dx\; \; \; \; =\int \! \frac{e^{-x}}{e^{-x}+1}dx                ....(1)

Let

        e^{-x}+1=t

        e^{-x}dx=-dt

From (1)

        \int \! \frac{-dt}{t}=-log\left | t \right |+C

        =-log\left | e^{-x}+1 \right |+C

Posted by

Gurleen Kaur

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