JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Self Evaluation Test - Trigonometric Function

  • question_answer
    If \[0\le x\le 2\pi ,\] then number of roots of equation \[{{e}^{\sin x}}-{{e}^{-\sin x}}=4\]is                                

    A) 0                     

    B) 1    

    C) 2                     

    D) 4

    Correct Answer: A

    Solution :

    The given equation can be written as \[{{e}^{\sin x}}=4+\frac{1}{{{e}^{\sin x}}}\]                        ?.(1) Now  \[-1\le \sin x\le 1\] and \[e<3\] \[\Rightarrow \,\,{{e}^{\sin x}}<3\] \[\Rightarrow \]  Again as we always have \[\frac{1}{{{e}^{\sin x}}}>0\] \[\therefore \,\,4+\frac{1}{{{e}^{\sin x}}}>4\] Thus the L.H.S of (1) \[<3\] and R.H.S of \[(1)>4.\] Hence there is no real values of x which satisfy (1). It follows that the given equation has no real solution.


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