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

  • question_answer
    \[{{\tan }^{-1}}\frac{3}{4}+{{\tan }^{-1}}\frac{3}{5}-{{\tan }^{-1}}\frac{8}{19}=\] [AMU 1976, 77]

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

    B) \[\frac{\pi }{3}\]

    C) \[\frac{\pi }{6}\]

    D) None of these

    Correct Answer: A

    Solution :

      \[{{\tan }^{-1}}\frac{3}{4}+{{\tan }^{-1}}\frac{3}{5}-{{\tan }^{-1}}\frac{8}{19}\] \[={{\tan }^{-1}}\left[ \frac{\frac{3}{4}+\frac{3}{5}}{1-\frac{3}{4}\times \frac{3}{5}} \right]-{{\tan }^{-1}}\frac{8}{19}={{\tan }^{-1}}\frac{27}{11}-{{\tan }^{-1}}\frac{8}{19}\] \[={{\tan }^{-1}}\left[ \frac{\frac{27}{11}-\frac{8}{19}}{1+\frac{27}{11}\times \frac{8}{19}} \right]={{\tan }^{-1}}\left( \frac{425}{425} \right)={{\tan }^{-1}}(1)=\frac{\pi }{4}\].


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