J & K CET Engineering J and K - CET Engineering Solved Paper-2014

  • question_answer
    If \[{{\cos }^{-1}}(2-{{x}^{2}})/(1+{{x}^{2}})+{{\tan }^{-1}}x=\pi /2,\], then x is equal to?

    A)  \[0\]     

    B)  \[1\]      

    C)  \[\frac{1}{\sqrt{3}}\]     

    D)  \[\sqrt{3}\]

    Correct Answer: C

    Solution :

    \[cs{{o}^{1}}\frac{(1-{{x}^{2}})}{(1+{{x}^{2}})}+{{\tan }^{-1}}x=\frac{\pi }{2}\] \[\Rightarrow \] \[2{{\tan }^{-1}}x+{{\tan }^{-1}}x=\frac{\pi }{2}\] \[\Rightarrow \] \[3{{\tan }^{-1}}x=\frac{\pi }{2}\] \[\Rightarrow \] \[{{\tan }^{-1}}x=\frac{\pi }{6}\] \[\Rightarrow \] \[x=\tan \frac{\pi }{6}\] \[\Rightarrow \] \[x=\frac{1}{\sqrt{3}}\]


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