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

  • question_answer
    \[\int_{0}^{\pi }{x}\,f\,(\sin x)\,dx=\]     [IIT 1982; Kurukshetra CEE 1993]

    A)                 \[\pi \int_{0}^{\pi }{f(\sin x)\,dx}\]         

    B)                 \[\frac{\pi }{2}\int_{0}^{\pi }{f(\sin x)\,dx}\]

    C)                 \[\frac{\pi }{2}\int_{0}^{\pi /2}{f(\sin x)\,dx}\]  

    D)                 None of these

    Correct Answer: B

    Solution :

               \[\int_{0}^{\pi }{x}f(\sin x)dx=\frac{\pi }{2}\int_{0}^{\pi }{f(\sin x)dx}\]                                 Since \[\int_{0}^{a}{xf(x)dx=\frac{1}{2}a\int_{0}^{a}{f(x)dx,}}\]if\[f(a-x)=f(x)\].


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