JEE Main & Advanced Mathematics Definite Integration Question Bank Fundamental definite integration, Definite integration by substitution

  • question_answer
    The value of \[\int_{1/e}^{\tan x}{\frac{t\,dt}{1+{{t}^{2}}}}+\int_{1/e}^{\cot x}{\frac{dt}{t(1+{{t}^{2}})}}=\]        [IIT Screening]

    A)                 \[-1\]    

    B)                 1

    C)                 0             

    D)                 None of these

    Correct Answer: B

    Solution :

               On integrating both functions, we get                    \[=\frac{1}{2}\left| \log (1+{{t}^{2}}) \right|_{1/e}^{\tan x}+\left| \left\{ \log t-\frac{1}{2}\log (1+{{t}^{2}}) \right\} \right|_{1/e}^{\cot x}\]                    \[=\frac{1}{2}\left[ \log {{\sec }^{2}}x-\log \left( 1+\frac{1}{{{e}^{2}}} \right) \right]+\log \cot x-\log \left( \frac{1}{e} \right)\]                      \[-\frac{1}{2}\left\{ \log (\text{cose}{{\text{c}}^{2}}x)-\log \left( 1+\frac{1}{{{e}^{2}}} \right) \right\}\]\[=-\log \left( \frac{1}{e} \right)=\log e=1\].


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