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

  • question_answer
    \[\int_{-\pi }^{\pi }{{{(\cos px-\sin qx)}^{2}}dx}\] is equal to (where \[p\] and \[q\] are integers) [IIT 1992]

    A)                 \[-\pi \]

    B)                 0

    C)                 \[\pi \] 

    D)                 \[2\pi \]

    Correct Answer: D

    Solution :

               \[I=\int_{-\pi }^{\pi }{({{\cos }^{2}}px+{{\sin }^{2}}qx-2\sin qx\cos px)dx}\]              \[=\int_{-\pi }^{\pi }{({{\cos }^{2}}px+{{\sin }^{2}}qx)dx-2\int_{-\pi }^{\pi }{\sin qx\cos px\,dx}}\]              \[=2\int_{0}^{\pi }{({{\cos }^{2}}px+{{\sin }^{2}}qx)dx-0}\]                   \[y=4x-{{x}^{2}}\].


You need to login to perform this action.
You will be redirected in 3 sec spinner