JCECE Engineering JCECE Engineering Solved Paper-2010

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

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

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

    C) \[x\]                                     

    D)  None of these

    Correct Answer: C

    Solution :

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


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