JEE Main & Advanced Mathematics Definite Integration Question Bank Properties of Definite Integration

  • question_answer
    \[\int_{0}^{\pi /2}{\,\,\log \tan x\,dx=}\]               [MP PET 1999; RPET 2001, 02; Karnataka CET 1999, 2000, 01, 02]

    A)                 \[\frac{\pi }{2}{{\log }_{e}}2\]    

    B)                 \[-\frac{\pi }{2}{{\log }_{e}}2\]

    C)                 \[\pi {{\log }_{e}}2\]      

    D)                 0

    Correct Answer: D

    Solution :

               \[\int_{0}^{\pi /2}{\log \tan x\,dx=}\int_{0}^{\pi /2}{\log \left( \frac{\sin x}{\cos x} \right)dx}\]                    \[=\int_{0}^{\pi /2}{\log \sin x\,dx-\int_{0}^{\pi /2}{\log \cos x\,dx=0}}\],                 \[\left\{ \because \int_{0}^{a}{f(x)dx=\int_{0}^{a}{f(a-x)dx}} \right\}\].


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