JEE Main & Advanced Sample Paper JEE Main Sample Paper-40

  • question_answer
    Value of \[\int_{0}^{\pi }{{{\sin }^{n}}x{{\cos }^{2m+1}}}xdx\]( where \[m,n\in N\]) is

    A) \[\frac{(2m+1)!}{n!}\]                       

    B) \[\frac{(2m+1)!}{{{n}^{2}}}\]

    C) \[\int_{0}^{\pi }{{{\cos }^{2m+!}}}xdx\]           

    D) none of these

    Correct Answer: D

    Solution :

    \[I=\int_{0}^{\pi }{{{\sin }^{n}}}x{{\cos }^{2m+1}}xdx\] \[=\int_{0}^{\pi }{{{\sin }^{n}}}(\pi -x).{{\cos }^{2m+1}}(\pi -x)dx\] \[=-\int_{0}^{\pi }{{{\sin }^{n}}}x{{\cos }^{2m+1}}xdx=-I\Rightarrow i=0\] Similarly, one can show that \[\int_{0}^{\pi }{{{\cos }^{2m+1}}}xdx=0\]


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