Manipal Engineering Manipal Engineering Solved Paper-2013

  • question_answer
    The interval for which\[2{{\tan }^{-1}}+{{\sin }^{-1}}\frac{2x}{1+{{x}^{2}}}\]is independent of\[x\]is

    A) \[|x|\,\,<1\]                     

    B) \[|x|\,\,>1\]

    C) \[|x|\,\,=1\]     

    D)        \[\phi \]

    Correct Answer: B

    Solution :

    We know that; if\[|x|\,\,\le 1\], then\[2{{\tan }^{-1}}x={{\sin }^{-1}}\left( \frac{2x}{1+{{x}^{2}}} \right)\] and if\[|x|\,\,>1\], then\[\pi -2{{\tan }^{-1}}x={{\sin }^{-1}}\left( \frac{2x}{1+{{x}^{2}}} \right)\] thus, if\[|x|\,\,>1\] \[2{{\tan }^{-1}}x+{{\sin }^{-1}}\frac{2x}{1+{{x}^{2}}}=2{{\tan }^{-1}}x+\pi \]                                                                 \[-2{{\tan }^{-1}}x=\pi \] which is independent of\[x\]


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