JEE Main & Advanced Mathematics Differentiation Question Bank Differentiation by Substitution

  • question_answer
    Differential coefficient of \[{{\tan }^{-1}}\sqrt{\frac{1-{{x}^{2}}}{1+{{x}^{2}}}}\] w.r.t. \[{{\cos }^{-1}}({{x}^{2}})\] is                     [RPET 1996]

    A)  \[\frac{1}{2}\]

    B)            \[-\frac{1}{2}\]

    C)            1

    D)            0

    Correct Answer: A

    Solution :

               Let \[y={{\tan }^{-1}}\sqrt{\frac{1-{{x}^{2}}}{1+{{x}^{2}}}}\]and \[z={{\cos }^{-1}}({{x}^{2}})\]            Put \[{{x}^{2}}=\cos 2\theta \];\[\therefore y={{\tan }^{-1}}\sqrt{\frac{2{{\sin }^{2}}\theta }{2{{\cos }^{2}}\theta }}=\theta \]and \[z=2\theta \]            \[\therefore \frac{dy}{dz}=\frac{dy/d\theta }{dz/d\theta }=\frac{1}{2}\].


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