CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2002

  • question_answer
    \[\int_{0}^{1}{\frac{d}{dx}}\left[ {{\sin }^{-1}}\left( \frac{2x}{1+{{x}^{2}}} \right) \right]dx\]is equal to:

    A)  \[0\]

    B)                                                         \[\pi \]

    C)         \[\frac{\pi }{2}\]                             

    D)         \[\frac{\pi }{4}\]

    E)         \[-\pi \]

    Correct Answer: C

    Solution :

                    Let \[I=\int_{0}^{1}{\frac{d}{dx}}\left[ {{\sin }^{-1}}\left( \frac{2x}{1+{{x}^{2}}} \right) \right]dx\] Let \[x=tan\theta \] \[\therefore \]  \[I=\int_{0}^{1}{\frac{d}{dx}}[{{\sin }^{-1}}(\sin 2\theta )]dx\]                 \[=2\int_{0}^{1}{\frac{d}{dx}}[{{\tan }^{-1}}x]\,dx\]                 \[=2[{{\tan }^{-1}}(1)-{{\tan }^{-1}}(0)]\]                 \[=2.\frac{\pi }{4}=\frac{\pi }{2}\]


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