JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Integration by Parts

  • question_answer
    \[\int_{{}}^{{}}{{{e}^{x}}\sin x\ dx=}\]    [IIT 1978; AI CBSE 1980; MP PET 1999]

    A)                 \[\frac{1}{2}{{e}^{x}}(\sin x+\cos x)+c\]

    B)                 \[\frac{1}{2}{{e}^{x}}(\sin x-\cos x)+c\]

    C)                 \[{{e}^{x}}(\sin x+\cos x)+c\]

    D)                 \[{{e}^{x}}(\sin x-\cos x)+c\]

    Correct Answer: B

    Solution :

                    Let \[I=\int_{{}}^{{}}{{{e}^{x}}\sin x\,dx}={{e}^{x}}\sin x-\int_{{}}^{{}}{{{e}^{x}}\cos x\,dx+c}\]                         \[={{e}^{x}}\sin x-{{e}^{x}}\cos x-\int_{{}}^{{}}{{{e}^{x}}\sin x\,dx+c}\]                 Þ \[2I={{e}^{x}}(\sin x-\cos x)+c\]Þ\[I=\frac{1}{2}{{e}^{x}}(\sin x-\cos x)+c\].


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