JEE Main & Advanced Mathematics Definite Integration Question Bank Summation of series by Definite Integration, Gamma function, Leibnitz's rule

  • question_answer
    \[\int_{0}^{\pi /2}{{{\cos }^{2}}x\,dx=}\]

    A)                 \[1-\frac{\pi }{4}\]          

    B)                 \[1+\frac{\pi }{4}\]

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

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

    Correct Answer: C

    Solution :

                       Using gamma function,                 \[\int_{0}^{\pi /2}{\,\,{{\cos }^{2}}x\,dx}\]=\[\frac{\Gamma \left( \frac{3}{2} \right)\Gamma \left( \frac{1}{2} \right)}{2\Gamma (2)}=\frac{\frac{1}{2}\Gamma \left( \frac{1}{2} \right)\Gamma \left( \frac{1}{2} \right)}{2.1.\Gamma (1)}=\frac{\pi }{4}\].


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