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

  • question_answer
    \[\int_{0}^{1}{\log \sin \left( \frac{\pi }{2}x \right)}\,dx=\]           [RPET 1997]

    A)                 \[-\log 2\]           

    B)                 \[\log 2\]

    C)                 \[\frac{\pi }{2}\log 2\]   

    D)                 \[-\frac{\pi }{2}\log 2\]

    Correct Answer: A

    Solution :

                Put \[\frac{\pi }{2}x=\theta \Rightarrow dx=\frac{2}{\pi }d\theta \]; As \[x=0\] to \[1,\] \[\theta =0\] to \[\frac{\pi }{2}\]                    Then it reduces to \[\frac{2}{\pi }\int_{0}^{\pi /2}{\,\,\log \sin \theta \,d\theta =\frac{2}{\pi }\left[ -\frac{\pi }{2}\log 2 \right]}\]                                                                                  \[=-\log 2\].


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