BCECE Engineering BCECE Engineering Solved Paper-2008

  • question_answer
    \[f(x)={{e}^{x}}\sin x,\]then \[f(x)\]is equal to

    A) \[{{e}^{6x}}\sin 6x\]            

    B)         \[2{{e}^{x}}\cos x\]            

    C)         \[8{{e}^{x}}\sin x\]             

    D)         \[8{{e}^{x}}\cos x\]

    Correct Answer: B

    Solution :

    \[f(x)={{e}^{x}}\sin x\] On differentiating w.r.t. x, we get                 \[f(x)={{e}^{x}}\cos x+\sin x{{e}^{x}}\] Again differentiating, w.r.t. \[x,\]we get                 \[f\,(x)={{e}^{x}}\cos x-{{e}^{x}}\sin x+{{e}^{x}}\sin x\]                                                 \[+\,{{e}^{x}}\cos x\]                                                 \[=2{{e}^{x}}\cos x\]


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