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JEE Main & Advanced JEE Main Online Paper (Held On 23 April 2013)

  • question_answer
                    The number of solutions of the equation\[\sin 2x-2\cos x+4\sin x=4\]in the interval\[[0,5\pi ]\]is:     JEE Main Online Paper ( Held On 23  April 2013 )

    A)                   3                           

    B)                                          5

    C)                                          4                                           

    D)                                          6

    Correct Answer: A

    Solution :

                     \[\sin 2x-2\cos x+4\sin x=4\] \[\Rightarrow \]\[2\sin x.\cos x-2\cos x+4\sin x-4=0\] \[\Rightarrow \]\[(\sin x-1)(\cos x-2)=0\] \[\because \]\[\cos x-2\ne 0,\therefore \sin x=1\] \[\therefore \]\[\frac{\pi }{2},\frac{5\pi }{2},\frac{9\pi }{2}\]


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