JEE Main & Advanced Mathematics Differentiation Question Bank Derivative at a point Standard Differentiation

  • question_answer
    \[\frac{d}{dx}\left\{ \log \left( \frac{{{e}^{x}}}{1+{{e}^{x}}} \right) \right\}=\]   

    A)            \[\frac{1}{1-{{e}^{x}}}\]

    B)            \[-\frac{1}{1+{{e}^{x}}}\]

    C)            \[-\frac{1}{1-{{e}^{x}}}\]

    D)            None of these

    Correct Answer: D

    Solution :

               \[\frac{d}{dx}\log \left( \frac{{{e}^{x}}}{1+{{e}^{x}}} \right)=\frac{1+{{e}^{x}}}{{{e}^{x}}}\times \frac{d}{dx}\left( \frac{{{e}^{x}}}{1+{{e}^{x}}} \right)\]                                                                           \[=\frac{1+{{e}^{x}}}{{{e}^{x}}}\times \frac{{{e}^{x}}}{{{(1+{{e}^{x}})}^{2}}}=\frac{1}{1+{{e}^{x}}}\].


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