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

  • question_answer
    Solve \[{{\sin }^{-1}}\,2x+{{\cos }^{-1}}\,2x+2\,{{\tan }^{-1}}\,x=\pi \]

    A)  \[1\]     

    B)  \[0\]     

    C)  \[-1\]    

    D)  \[1/\sqrt{2}\]

    Correct Answer: A

    Solution :

    We have, \[{{\sin }^{-1}}\,2x+{{\cos }^{-1}}2x+2{{\tan }^{-1}}x=x\] \[\Rightarrow \]  \[\frac{\pi }{2}+2{{\tan }^{-1}}x=\pi \,\left( \because \,\,\,{{\sin }^{-1}}x+{{\cos }^{-1}}x=\frac{\pi }{2} \right)\] \[\Rightarrow \] \[2{{\tan }^{-1}}x=\frac{\pi }{1}-\frac{\pi }{2}=\frac{\pi }{2}\] \[\Rightarrow \] \[{{\tan }^{-1}}x=\frac{\pi }{4}\] \[\Rightarrow \] \[x=\tan \frac{\pi }{4}\] \[\Rightarrow \] \[x=1\]


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