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

  • question_answer
     is equal to          [RPET 2000]

    A)                 \[-{{e}^{x}}\tan \,\left( x/2 \right)\]

    B)                 \[-{{e}^{x}}\cot \,\left( x/2 \right)\]

    C)                 \[-\frac{1}{2}{{e}^{x}}\tan \,\left( \frac{x}{2} \right)\]

    D)  \[\frac{1}{2}{{e}^{x}}\cot \,\left( \frac{x}{2} \right)\]

    Correct Answer: B

    Solution :

                    \[I=\int{{{e}^{x}}\left( \frac{1-\sin x}{1-\cos x} \right)dx}\]\[=\int{{{e}^{x}}\left( \frac{1-\sin x}{2{{\sin }^{2}}(x/2)} \right)\,dx}\]                 Þ \[I=\int{{{e}^{x}}\left( \frac{1}{2}\text{cose}{{\text{c}}^{2}}\frac{x}{2}-\cot \frac{x}{2} \right)}\,dx\] \[\left( \because \,\,\int{{{e}^{x}}\left( f(x)+f'(x) \right)}={{e}^{x}}f(x)+c \right)\]                 \[\therefore \,\,I={{e}^{x}}\left( -\cot \frac{x}{2} \right)+c=-{{e}^{x}}\cot \frac{x}{2}+c\].


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