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

  • question_answer
    \[\int_{\,0}^{\,\pi }{\log {{\sin }^{2}}x\,dx=}\]                                    [MP PET 1997]

    A)                 \[2\pi {{\log }_{e}}\left( \frac{1}{2} \right)\]        

    B)                 \[\pi {{\log }_{e}}2+c\]

    C)                 \[\frac{\pi }{2}{{\log }_{e}}\left( \frac{1}{2} \right)+c\]   

    D)                 None of these

    Correct Answer: A

    Solution :

               \[\int_{0}^{\pi }{2\log \sin xdx=2\int_{0}^{2\frac{\pi }{2}}{\log \sin xdx=4\int_{0}^{\pi /2}{\log \sin x\,dx}}}\]                                 \[=4\times \left( -\frac{\pi }{2}\log 2 \right)=-2\pi {{\log }_{e}}2=2\pi {{\log }_{e}}\left( \frac{1}{2} \right)\].


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