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

  • question_answer
    \[\cos \left[ {{\tan }^{-1}}\frac{1}{3}+{{\tan }^{-1}}\frac{1}{2} \right]=\] [MP PET 1991; MNR 1990]

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

    B) \[\frac{\sqrt{3}}{2}\]

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

    D) \[\frac{\pi }{4}\]

    Correct Answer: A

    Solution :

      \[\cos \,\left[ {{\tan }^{-1}}\frac{1}{3}+{{\tan }^{-1}}\frac{1}{2} \right]=\cos \,\left[ {{\tan }^{-1}}\left( \frac{\frac{1}{3}+\frac{1}{2}}{1-\frac{1}{3}\times \frac{1}{2}} \right) \right]\] \[=\cos \,\{{{\tan }^{-1}}(1)\}=\cos \frac{\pi }{4}=\frac{1}{\sqrt{2}}\].


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