Manipal Engineering Manipal Engineering Solved Paper-2008

  • question_answer
    If\[\alpha ={{\sin }^{-1}}\frac{\sqrt{3}}{2}+{{\sin }^{-1}}\frac{1}{3}\]and\[\beta ={{\cos }^{-1}}\frac{\sqrt{3}}{2}+{{\cos }^{-1}}\frac{1}{3}\], then

    A) \[\alpha >\beta \]                           

    B) \[\alpha =\beta \]

    C) \[\alpha <\beta \]           

    D)        \[\alpha +\beta =2\pi \]

    Correct Answer: C

    Solution :

    Now,\[\alpha +\beta ={{\sin }^{-1}}\frac{\sqrt{3}}{2}+{{\cos }^{-1}}\frac{\sqrt{3}}{2}\]                                                 \[+{{\sin }^{-1}}\frac{1}{3}+{{\cos }^{-1}}\frac{1}{3}\]                 \[=\frac{\pi }{2}+\frac{\pi }{2}=\pi \] Also,      \[\alpha =\frac{\pi }{3}+{{\sin }^{-1}}\frac{1}{3}<\frac{\pi }{3}+{{\sin }^{-1}}\frac{1}{2}\] As\[\sin \theta \]is increasing in\[\left[ 0,\,\,\frac{\pi }{2} \right]\]. \[\therefore \]  \[\alpha <\frac{\pi }{3}+\frac{\pi }{6}=\frac{\pi }{2}\] \[\Rightarrow \]               \[\beta >\frac{\pi }{2}>\alpha \] \[\Rightarrow \]               \[\alpha <\beta \]


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