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

  • question_answer
    \[\tan ({{\cos }^{-1}}x)\] is equal to     [IIT 1993]

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

    B) \[\frac{x}{1+{{x}^{2}}}\]

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

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

    Correct Answer: A

    Solution :

      Let \[{{\cos }^{-1}}x=\theta .\] Then \[x=\cos \theta \] \[\Rightarrow \,\,\tan \theta =\sqrt{{{\sec }^{2}}\theta -1}\]\[=\sqrt{\frac{1}{{{x}^{2}}}-1}=\sqrt{\frac{1-{{x}^{2}}}{x}}\] \[\therefore \,\,\tan \,({{\cos }^{-1}}x)=\tan \theta =\frac{\sqrt{1-{{x}^{2}}}}{x}\].


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