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JEE Main & Advanced JEE Main Paper (Held on 12-4-2019 Morning)

  • question_answer
    The number of solutions of the equation \[1+{{\sin }^{4}}x={{\cos }^{2}}3x,x\in \left[ -\frac{5\pi }{2},\frac{5\pi }{2} \right]\]is: [JEE Main Held on 12-4-2019 Morning]

    A) 5

    B) 4

    C) 7                                 

    D) 3

    Correct Answer: A

    Solution :

    \[1+{{\sin }^{4}}x={{\cos }^{2}}3x\]           \[\sin x=0\And \cos 3x=1\]           \[0,2\pi ,-2\pi ,-\pi ,\pi \]                             


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