JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Integration by Substitution

  • question_answer
    The value of \[\int_{{}}^{{}}{\frac{{{e}^{x}}}{{{e}^{x}}+1}}\,dx\] is            [Pb. CET 2000]

    A)            \[{{e}^{x}}+c\]

    B)            \[({{e}^{x}}+1)+c\]

    C)                    \[\log ({{e}^{x}}+1)+c\]

    D)  None of these

    Correct Answer: C

    Solution :

                       Put \[{{e}^{x}}+1=t\Rightarrow {{e}^{x}}dx=dt\]                                                               \[\therefore \] \[\int_{{}}^{{}}{\frac{{{e}^{x}}}{{{e}^{x}}+1}dx=\int_{{}}^{{}}{\frac{dt}{t}=\log t+c=\log ({{e}^{x}}+1)+c}}\].


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