Manipal Engineering Manipal Engineering Solved Paper-2009

  • question_answer
    \[{{\cos }^{-1}}\left( \frac{-1}{2} \right)-2{{\sin }^{-1}}\left( \frac{1}{2} \right)+3{{\cos }^{-1}}\left( \frac{-1}{\sqrt{2}} \right)\]\[-4{{\tan }^{-1}}(-1)\]equals

    A) \[\frac{19\pi }{12}\]                                       

    B) \[\frac{35\pi }{12}\]

    C) \[\frac{47\pi }{12}\]                       

    D)        \[\frac{43\pi }{12}\]

    Correct Answer: D

    Solution :

    \[{{\cos }^{-1}}\left( -\frac{1}{2} \right)-2{{\sin }^{-1}}\left( \frac{1}{2} \right)+3{{\cos }^{-1}}\left( -\frac{1}{\sqrt{2}} \right)\]                                                                 \[-4{{\tan }^{-1}}(-1)\] \[=\pi -{{\cos }^{-1}}\left( \frac{1}{2} \right)-2\left( \frac{\pi }{6} \right)+3\left( \pi -{{\cos }^{-1}}\left( \frac{1}{\sqrt{2}} \right) \right)\]                                                                 \[+4{{\tan }^{-1}}(1)\]                 \[=\pi -\frac{\pi }{3}-\frac{\pi }{3}+3\left( \pi -\frac{\pi }{4} \right)+4\cdot \frac{\pi }{4}\]                 \[\frac{\pi }{3}+3\cdot \frac{3\pi }{4}+\pi \]                 \[=\frac{43\pi }{12}\]


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