JEE Main & Advanced Mathematics Inverse Trigonometric Functions Question Bank Self Evaluation Test - Inverse Trigonometric Functions

  • question_answer
    If \[{{\sin }^{-1}}(x-1)+co{{s}^{-1}}(x-3)+ta{{n}^{-1}}\left( \frac{x}{2-{{x}^{2}}} \right)\]\[={{\cos }^{-1}}k+\pi ,\] Then the value of k is

    A) 1

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

    C) \[\frac{1}{\sqrt{2}}\]

    D) None of these

    Correct Answer: C

    Solution :

    [c] \[{{\sin }^{-1}}(x-1)\Rightarrow -1\le x-1\le 1\Rightarrow 0\le x\le 2\] \[{{\cos }^{-1}}(x-3)\Rightarrow -1\le x-3\le 1\Rightarrow 2\le x\le 4\] \[\therefore x=2\] So, \[{{\sin }^{-1}}(2-1)+co{{s}^{-1}}(2-3)+ta{{n}^{-1}}\frac{2}{2-4}\] \[={{\cos }^{-1}}k+\pi \] Or \[{{\sin }^{-1}}1+{{\cos }^{-1}}(-1)+ta{{n}^{-1}}(-1)=co{{s}^{-1}}k+\pi \] \[\Rightarrow \frac{\pi }{2}+\pi -\frac{\pi }{4}={{\cos }^{-1}}k+\pi \Rightarrow {{\cos }^{-1}}k=\frac{\pi }{4}\]or \[k=\frac{1}{\sqrt{2}}\]


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