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

  • question_answer
    \[\int_{{}}^{{}}{{{e}^{2x}}(-\sin x+2\cos x)\ dx=}\] [DSSE 1987]

    A)                 \[{{e}^{2x}}\sin x+c\]

    B)                 \[-{{e}^{2x}}\sin x+c\]

    C)                 \[-{{e}^{2x}}\cos x+c\]

    D)                 \[{{e}^{2x}}\cos x+c\]

    Correct Answer: D

    Solution :

                    \[\int_{{}}^{{}}{{{e}^{2x}}(-\sin x+2\cos x)\,dx}\]                        \[=-\int_{{}}^{{}}{{{e}^{2x}}\sin x\,dx}+2\int_{{}}^{{}}{{{e}^{2x}}\cos x\,dx}\]                        \[={{e}^{2x}}\cos x-2\int_{{}}^{{}}{{{e}^{2x}}\cos x\,dx+2\int_{{}}^{{}}{{{e}^{2x}}\cos x\,dx+c}}\]                        \[={{e}^{2x}}\cos x+c.\]                 Aliter : \[\int_{{}}^{{}}{{{e}^{2x}}(2\cos x-\sin x)\,dx}={{e}^{2x}}\cos x+c\]          \[\left\{ \because \,\,\,\int_{{}}^{{}}{{{e}^{kx}}\left\{ k\,f(x)+{f}'(x) \right\}dx={{e}^{kx}}f(x)+c} \right\}\]


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