J & K CET Engineering J and K - CET Engineering Solved Paper-2011

  • question_answer
    The value of the integral \[\int{\frac{1}{{{e}^{2s}}+{{e}^{-2x}}}}\,\,dx\] is equal to

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

    B)  \[{{\tan }^{-1}}\,({{e}^{2x}})+C\]

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

    D)  \[\frac{-1}{{{({{e}^{2x}}+{{e}^{-2x}})}^{2}}}+C\]

    Correct Answer: C

    Solution :

    \[\int{\frac{dx}{{{e}^{2x}}+{{e}^{-2x}}}}\Rightarrow \,\int{\frac{{{e}^{2x}}}{{{e}^{4x}}+1}}dx\] \[=\int{\frac{{{e}^{2x}}}{1+{{({{e}^{2x}})}^{2}}}}dx,\] put \[t={{e}^{2x}}\] \[dt=2{{e}^{2x}}\,dx\] \[\Rightarrow \] \[\int{\frac{dt}{2(1+{{t}^{2}})}}=\frac{1}{2}{{\tan }^{-1}}t+C\] \[\Rightarrow \] \[=\frac{1}{2}{{\tan }^{-1}}({{e}^{2x}})+C\]


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