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

  • question_answer
    The value of \[\int_{a}^{a+(\pi /2)}{({{\sin }^{4}}x+{{\cos }^{4}}x)\,dx}\] is

    A)                 Independent of \[a\]    

    B)                 \[a\,{{\left( \frac{\pi }{2} \right)}^{2}}\]

    C)                 \[\frac{3\pi }{8}\]            

    D)                 \[\frac{3\pi {{a}^{2}}}{8}\]

    Correct Answer: C

    Solution :

                       Since \[{{\sin }^{4}}x+{{\cos }^{4}}x\]is a periodic function with period \[\frac{\pi }{2},\] therefore \[\int_{a}^{a+(\pi /2)}{({{\sin }^{4}}x+{{\cos }^{4}}x)\text{ }dx}\]                    \[=\int_{0}^{\pi /2}{({{\sin }^{4}}x+{{\cos }^{4}}x)dx}\]                                 \[=2\int_{0}^{\pi /2}{{{\sin }^{4}}x\,dx=\frac{3\Gamma (5/2)\Gamma (1/2)}{2\Gamma \left( \frac{4+0+2}{2} \right)}=\frac{3\pi }{8}}\].


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