Manipal Engineering Manipal Engineering Solved Paper-2011

  • question_answer
    The number of values of\[x\]in the interval\[[0,\,\,5\pi ]\]satisfying the equation\[3{{\sin }^{2}}x-7\sin x+2=0\]is

    A)  0                                            

    B)  5

    C)  6                            

    D)         10

    Correct Answer: C

    Solution :

    Given,\[3{{\sin }^{2}}x-7\sin x+2=0\] \[\Rightarrow \]\[(2\sin x-1)(\sin x-2)=0\] \[\Rightarrow \]\[\sin x=\frac{1}{3}\]                     \[(\because \,\,\sin x\ne 2)\] Let\[{{\sin }^{-1}}\frac{1}{3}=\alpha ,\,\,0<\alpha <\frac{\pi }{2}\]are the solutions in\[[0,\,\,5\pi ]\]. Then, \[\alpha ,\,\,\pi -\alpha ,\,\,2\pi +\alpha ,\,\,3\pi -\alpha ,\,\,4\pi +\alpha ,\,\,5\pi -\alpha \]are the solutions.


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