J & K CET Engineering J and K - CET Engineering Solved Paper-2011

  • question_answer
    The value of \[\tan \left[ {{\cos }^{-1}}\left( \frac{3}{5} \right)+{{\tan }^{-1}}\left( \frac{2}{3} \right) \right]\] is

    A)  \[6\]              

    B)  \[17/6\]

    C)  \[6/17\]           

    D)  None of these

    Correct Answer: D

    Solution :

    \[\tan \left[ {{\cos }^{-1}}\left( \frac{3}{5} \right)+{{\tan }^{-1}}\left( \frac{2}{3} \right) \right]\] \[=\tan \left[ {{\sec }^{-1}}\left( \frac{5}{3} \right)+{{\tan }^{-1}}\left( \frac{2}{3} \right) \right]\] \[=\tan \left[ {{\tan }^{-1}}\sqrt{-1+{{\left( \frac{5}{3} \right)}^{2}}}+{{\tan }^{-1}}\left( \frac{2}{3} \right) \right]\] \[=\tan \left[ {{\tan }^{-1}}\left( \frac{4}{3} \right)+{{\tan }^{-1}}\left( \frac{2}{3} \right) \right]\] \[=\tan \left[ {{\tan }^{-1}}\left( \frac{\frac{4}{3}+\frac{2}{3}}{1-\frac{4}{3}.\frac{2}{3}} \right) \right]=\frac{\frac{6}{3}}{\frac{1}{9}}\] \[\Rightarrow \] \[\frac{6}{3}\times 9=18\]


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