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

  • question_answer
    If \[\int_{{}}^{{}}{\frac{{{e}^{x}}(1+\sin x)dx}{1+\cos x}={{e}^{x}}f(x)+c}\], then \[f(x)=\]             [RPET 1997; Karnataka CET 2003, 05; Orissa JEE 2004]

    A)                 \[\sin \frac{x}{2}\]

    B)                 \[\cos \frac{x}{2}\]

    C)                 \[\tan \frac{x}{2}\]

    D)                 \[\log \frac{x}{2}\]

    Correct Answer: C

    Solution :

                    \[I=\int_{{}}^{{}}{{{e}^{x}}\left( \frac{1+\sin x}{1+\cos x} \right)\,dx}=\int_{{}}^{{}}{{{e}^{x}}\left[ \frac{1+2\sin (x/2)\,\cos (x/2)}{2{{\cos }^{2}}(x/2)} \right]dx}\]                 \[I=\int_{{}}^{{}}{{{e}^{x}}\left[ \frac{1}{2}{{\sec }^{2}}(x/2)+\tan (x/2) \right]\,dx}={{e}^{x}}.\tan (x/2)+c\]              \[\{\because \,\,\,\int_{{}}^{{}}{{{e}^{x}}[f(x)+{f}'(x)\,]dx={{e}^{x}}.\,f(x)+c\}}\]


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