JEE Main & Advanced Mathematics Differentiation Question Bank Differentiation by Substitution

  • question_answer
    If \[y={{\sin }^{-1}}\frac{2x}{1+{{x}^{2}}},\]where \[0<x<1\]and \[0<y<\frac{\pi }{2},\] then \[\frac{dy}{dx}=\]  

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

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

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

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

    Correct Answer: A

    Solution :

               \[y={{\sin }^{-1}}\frac{2x}{1+{{x}^{2}}}\]            Put \[x=\tan \theta \]            \[x\]            \[y=2\theta =2{{\tan }^{-1}}x\]            \[(\because \theta ={{\tan }^{-1}}x)\]            Differentiating with respect to x, we get             \[\frac{dy}{dx}=\frac{2}{1+{{x}^{2}}}\]    \[\left( \text{Since }\,\,0<x<1\text{ and  }0<y<\frac{\pi }{2} \right)\].


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