JEE Main & Advanced Mathematics Inverse Trigonometric Functions Question Bank Inverse trigonometric functions

  • question_answer
    If \[{{\cos }^{-1}}\left( \frac{1}{x} \right)=\theta \], then \[\tan \theta \]= [MNR 1978; MP PET 1989]

    A) \[\frac{1}{\sqrt{{{x}^{2}}-1}}\]

    B)   \[\sqrt{{{x}^{2}}+1}\]

    C) \[\sqrt{1-{{x}^{2}}}\]

    D) \[\sqrt{{{x}^{2}}-1}\]

    Correct Answer: D

    Solution :

    Given that \[{{\cos }^{-1}}\left( \frac{1}{x} \right)=\theta \,\,\Rightarrow \,\,\cos \theta =\frac{1}{x}\] Now,  \[\tan \theta =\frac{\sin \theta }{\cos \theta }=\frac{\sqrt{1-{{(1/x)}^{2}}}}{1/x}=\sqrt{{{x}^{2}}-1}\]


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