CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2009

  • question_answer
    \[\int{\text{cosec (x-a) cosec x dx}}\] is equal to

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

    B)  \[{{e}^{{{\tan }^{-1}}x}}+c\]

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

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

    Correct Answer: A

    Solution :

    Let \[I=\int{{{e}^{{{\tan }^{-1}}x}}}\left( 1+\frac{x}{1+{{x}^{2}}} \right)dx\] \[=\int{{{e}^{{{\tan }^{-1}}x}}}dx+\int{\frac{x\,{{e}^{\tan -{{1}_{x}}}}}{1+{{x}^{2}}}}dx\] \[=x\,\,{{e}^{{{\tan }^{-1}}x}}-\int{\frac{x{{e}^{{{\tan }^{-1}}x}}}{1+{{x}^{2}}}}dx+\int{\frac{x{{e}^{{{\tan }^{-1}}x}}}{1+{{x}^{2}}}}dx+c\] \[=x{{e}^{{{\tan }^{-1}}x}}+c\]


You need to login to perform this action.
You will be redirected in 3 sec spinner