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

  • question_answer
    If \[y={{\tan }^{-1}}\left( \frac{\sqrt{x}-x}{1+{{x}^{3/2}}} \right),\]then \[y'(1)\] is              [AMU 2000]

    A)            0

    B)            \[\frac{1}{2}\]

    C)            ? 1

    D)            \[-\frac{1}{4}\]

    Correct Answer: D

    Solution :

               \[y={{\tan }^{-1}}\left( \frac{\sqrt{x}-x}{1+{{x}^{3/2}}} \right)={{\tan }^{-1}}(\sqrt{x})-{{\tan }^{-1}}(x)\]            Þ\[{y}'=\frac{1}{1+x}.\frac{1}{2\sqrt{x}}-\frac{1}{1+{{x}^{2}}}\Rightarrow {y}'(1)=\frac{1}{2}.\frac{1}{2}-\frac{1}{2}=\frac{-1}{4}\].


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