12th Class Mathematics Sample Paper Mathematics Olympiad - Sample Paper-3

  • question_answer
    \[\int{{{e}^{{{\tan }^{-1x}}}}}\left( 1+\frac{x}{1+{{x}^{2}}} \right)\]Is equal to:

    A) \[\frac{1}{2}x{{e}^{{{\tan }^{-1}}x}}+C\]                

    B) \[x.{{e}^{{{\tan }^{-1}}x}}+C\]      

    C) \[\frac{1}{2}.{{e}^{{{\tan }^{-1}}x}}+C\]    

    D) \[{{e}^{{{\tan }^{-1}}x}}+C\]

    Correct Answer: B

    Solution :

    [b] \[I=\int{{{e}^{{{\tan }^{-1}}x}}}\left( 1+\frac{x}{1+{{x}^{2}}} \right).dx=\int{{{e}^{{{\tan }^{-1}}x}}}.dx+\int{{{e}^{{{\tan }^{-1}}x}}}.\frac{x}{1+{{x}^{2}}}.dx\]\[={{e}^{{{\tan }^{-1}}x}}.x-\int{x.{{e}^{{{\tan }^{-1}}x}}}.\frac{1}{1+{{x}^{2}}}.dx+\int{{{e}^{{{\tan }^{-1}}x}}}.\frac{x}{1+{{x}^{2}}}.dx+c\]\[=x.{{e}^{{{\tan }^{-1}}x}}+c\] Hence, option [b] is correct.


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