BCECE Engineering BCECE Engineering Solved Paper-2003

  • question_answer
    If\[f(x)=x{{\tan }^{-1}}x,\] then \[f(1)\] is equal to:

    A) \[1+\frac{\pi }{4}\]

    B)                                         \[\frac{1}{2}+\frac{\pi }{4}\]

    C)                   \[\frac{1}{2}-\frac{\pi }{4}\]                       

    D)                   2

    Correct Answer: B

    Solution :

    \[f(x)=x\,{{\tan }^{-1}}x\] On differentiating both sides w.r.t. \[x,\] we get \[f(x)=x\frac{1}{1+{{x}^{2}}}+{{\tan }^{-1}}x\] \[f{{(x)}_{x=1}}=\frac{1}{1+{{1}^{2}}}+{{\tan }^{-1}}1\] \[=\frac{1}{2}+\frac{\pi }{4}\]


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