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

  • question_answer
    \[\frac{d}{dx}\left[ {{\tan }^{-1}}\left( \frac{a-x}{1+ax} \right) \right]=\] [Karnataka CET 2001; Pb. CET 2001]

    A)            \[-\frac{1}{1+{{x}^{2}}}\]

    B)            \[\frac{1}{1+{{a}^{2}}}-\frac{1}{1+{{x}^{2}}}\]

    C)            \[\frac{1}{1+{{\left( \frac{a-x}{1+ax} \right)}^{2}}}\]

    D)            \[\frac{-1}{\sqrt{1-{{\left( \frac{a-x}{1+ax} \right)}^{2}}}}\]

    Correct Answer: A

    Solution :

               \[\frac{d}{dx}\left[ {{\tan }^{-1}}\left( \frac{a-x}{1+ax} \right) \right].\]                    = \[\frac{d}{dx}[{{\tan }^{-1}}a-{{\tan }^{-1}}x]=0-\frac{1}{1+{{x}^{2}}}=-\frac{1}{1+{{x}^{2}}}\].


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