12th Class Mathematics Sample Paper Mathematics Olympiad - Sample Paper-1

  • question_answer
    \[\mathbf{co}{{\mathbf{s}}^{-1}}\left( \frac{1}{2} \right)+2si{{n}^{-1}}\left( \frac{1}{2} \right)\]- is equal to:

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

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

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

    D)  \[\frac{2\pi }{3}\]

    Correct Answer: D

    Solution :

    [d] \[\because {{\cos }^{-1}}\left( \frac{1}{2} \right)+2{{\sin }^{-1}}\left( \frac{1}{2} \right)\] \[={{\cos }^{-1}}\left( \cos \frac{\pi }{3} \right)+2{{\sin }^{-1}}\left( \sin \frac{\pi }{6} \right)=\frac{\pi }{3}+2.\frac{\pi }{6}=\frac{2\pi }{3}\]Hence, option [d] is correct.


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