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

  • question_answer
    \[\int_{{}}^{{}}{x{{\tan }^{-1}}}xdx=\]     [Roorkee 1979]

    A)                 \[\frac{1}{2}({{x}^{2}}+1){{\tan }^{-1}}x-\frac{1}{2}x+c\]

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

    C)                 \[\frac{1}{2}({{x}^{2}}+1){{\tan }^{-1}}x+\frac{1}{2}x+c\]              

    D)                 \[\frac{1}{2}({{x}^{2}}+1){{\tan }^{-1}}x-x+c\]

    Correct Answer: A

    Solution :

                    \[\int_{{}}^{{}}{x\,.\,{{\tan }^{-1}}x\,dx=\frac{{{x}^{2}}}{2}{{\tan }^{-1}}x-\frac{1}{2}\int_{{}}^{{}}{\frac{{{x}^{2}}+1-1}{1+{{x}^{2}}}\,dx}}\]                                            \[=\frac{{{x}^{2}}}{2}{{\tan }^{-1}}x-\frac{1}{2}x+\frac{1}{2}{{\tan }^{-1}}x+c\]                                            \[=\frac{1}{2}{{\tan }^{-1}}x\,.\,({{x}^{2}}+1)-\frac{1}{2}x+c\].


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