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

  • question_answer
    The value of \[\int_{0}^{\pi /4}{\frac{1+\tan x}{1-\tan x}\,dx}\] is                             [SCRA 1986]

    A)                 \[-\frac{1}{2}\log 2\]      

    B)                 \[\frac{1}{4}\log 2\]

    C)                 \[\frac{1}{3}\log 2\]       

    D)                 None of these

    Correct Answer: A

    Solution :

               \[\int_{0}^{\pi /4}{\frac{1+\tan x}{1-\tan x}dx=\int_{0}^{\pi /4}{\tan \left( \frac{\pi }{4}+x \right)\,dx}}\]                                 \[=\left[ \log \left\{ \sec \left( \frac{\pi }{4}+x \right) \right\} \right]_{0}^{-\pi /4}=-\frac{1}{2}\log 2\].


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