CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2009

  • question_answer
    The value of\[\cos [{{\tan }^{-1}}\{\sin ({{\cot }^{-1}}x)\}]\]is

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

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

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

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

    E)  \[\sqrt{\frac{1-{{x}^{2}}}{2-{{x}^{2}}}}\]              

    Correct Answer: D

    Solution :

    \[\cos [{{\tan }^{-1}}\{\sin ({{\cot }^{-1}}x)\}]\] \[=\cos \left[ {{\tan }^{-1}}\left\{ \sin \frac{1}{\sqrt{1+{{x}^{2}}}} \right\} \right]\] \[=\cos \left[ {{\tan }^{-1}}\frac{1}{\sqrt{1+{{x}^{2}}}} \right]\]                 \[=\cos \left[ {{\cos }^{-1}}\sqrt{\frac{1+{{x}^{2}}}{2+{{x}^{2}}}} \right]\]                 \[=\sqrt{\frac{1+{{x}^{2}}}{2+{{x}^{2}}}}\]


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