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

  • question_answer
    \[\int_{{}}^{{}}{\frac{{{e}^{m{{\tan }^{-1}}x}}}{1+{{x}^{2}}}dx}\] equals to            [RPET 2001]

    A)            \[{{e}^{{{\tan }^{-1}}x}}\]

    B)            \[\frac{1}{m}{{e}^{{{\tan }^{-1}}x}}\]

    C)            \[\frac{1}{m}{{e}^{m{{\tan }^{-1}}x}}\]

    D)   None of these

    Correct Answer: C

    Solution :

                       \[I=\int{\frac{{{e}^{m\,\,{{\tan }^{-1}}x}}}{1+{{x}^{2}}}dx}\],  Put \[m{{\tan }^{-1}}x=t\]            Þ \[\frac{m}{1+{{x}^{2}}}\,dx=dt\] Þ \[\frac{dx}{1+{{x}^{2}}}=\frac{dt}{m}\]            \[I=\frac{1}{m}\int{{{e}^{t}}.dt}\] \[=\frac{1}{m}{{e}^{t}}+c\] \[=\frac{1}{m}{{e}^{m\,{{\tan }^{-1}}x}}+c\].


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