JEE Main & Advanced Sample Paper JEE Main - Mock Test - 44

  • question_answer
    If \[\int\limits_{0}^{\pi }{x\,f\,(\sin \,\,x)dx=A\int\limits_{0}^{\pi /2}{f\,(\sin x)dx,}}\] then A is

    A) \[2\pi \]

    B)        \[\pi \]

    C) \[\frac{\pi }{4}\]

    D)        0

    Correct Answer: B

    Solution :

    Let \[=\int\limits_{0}^{\pi }{xf}(\sin x)dx=\int\limits_{0}^{\pi }{(\pi -x)f(\sin x)dx}\] \[\therefore \,\,2I=\pi \int\limits_{0}^{\pi }{f(\sin x)dx=\pi .2\int\limits_{0}^{\frac{\pi }{2}}{f(\sin x)\,dx}}\] \[\therefore \,I=\pi \int\limits_{0}^{\frac{\pi }{2}}{f\,(\sin x)dx\Rightarrow A=\pi }\]


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