RAJASTHAN ­ PET Rajasthan PET Solved Paper-2008

  • question_answer
    \[\int_{-a}^{a}{x\sqrt{({{a}^{2}}-{{x}^{2}})}}dx\]is equal to

    A)  \[\frac{\pi }{4}\]

    B)  \[\frac{\pi }{3}\]

    C)  \[\frac{\pi }{8}\]

    D)  \[0\]

    Correct Answer: D

    Solution :

     Let \[I=\int_{-a}^{a}{x}\sqrt{{{a}^{2}}-{{x}^{2}}}dx\] Again, let  \[f(x)=x\sqrt{{{a}^{2}}-{{x}^{2}}}\] \[f(-x)=-x\sqrt{{{a}^{2}}-{{x}^{2}}}\] \[=-f(x)\] \[\therefore \]\[f(x)\]is an odd function. Hence, \[I=0\]


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