JEE Main & Advanced Mathematics Differentiation Question Bank Differentiation by Substitution

  • question_answer
    Differential coefficient of \[\frac{{{\tan }^{-1}}x}{1+{{\tan }^{-1}}x}\] w.r.t. \[{{\tan }^{-1}}x\] is

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

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

    C)            \[\frac{1}{{{(1+{{\tan }^{-1}}x)}^{^{2}}}}\]

    D)            \[\frac{-1}{2\,{{(1+{{\tan }^{-1}}x)}^{2}}}\]

    Correct Answer: C

    Solution :

               The differential coefficient of \[\frac{{{\tan }^{-1}}x}{1+{{\tan }^{-1}}x}\] with respect to \[{{\tan }^{-1}}x=\frac{\frac{d}{dx}\left( \frac{{{\tan }^{-1}}x}{1+{{\tan }^{-1}}x} \right)}{\frac{d}{dx}({{\tan }^{-1}}x)}\]                     \[=\frac{(1+{{\tan }^{-1}}x)\frac{d}{dx}{{\tan }^{-1}}x-{{\tan }^{-1}}x\frac{d}{dx}(1+{{\tan }^{-1}}x)}{{{(1+{{\tan }^{-1}}x)}^{2}}.\frac{d}{dx}{{\tan }^{-1}}x}\]                     \[=\frac{1}{{{(1+{{\tan }^{-1}}x)}^{2}}}\].


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