J & K CET Engineering J and K - CET Engineering Solved Paper-2003

  • question_answer
    The  relation \[{{\tan }^{-1}}\left( \frac{1+x}{1-x} \right)=\frac{\pi }{4}+{{\tan }^{-1}}x\] holds true for all

    A)  \[x\,\in R\]

    B)  \[x\,\in (-\infty ,\,1)\]

    C)  \[x\,\in (-1,\,\,\infty )\]

    D)  \[x\,\in (-\,\infty ,-1)\]

    Correct Answer: B

    Solution :

    Given that, \[{{\tan }^{-1}}\left( \frac{1+x}{1-x} \right)=\frac{\pi }{4}+{{\tan }^{-1}}x\] \[RHS=\frac{\pi }{4}+{{\tan }^{-1}}x\] \[={{\tan }^{-1}}+{{\tan }^{-1}}x\] \[={{\tan }^{-1}}\left( \frac{1+x}{1-x} \right),\] if \[x<1\] \[\therefore \] \[x\,\,\in \,\,(-\infty ,\,\,1)\]


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