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

  • question_answer
    \[\int_{\,0}^{\,\pi }{\sqrt{\frac{1+\cos 2x}{2}}\,dx}\]  is equal to                                [AMU 2001]

    A)                 0             

    B)                 2

    C)                 1             

    D)                 \[-1\]

    Correct Answer: B

    Solution :

               \[I=\int_{0}^{\pi }{\sqrt{\frac{1+\cos 2x}{2}}dx=\int_{0}^{\,\pi }{|\cos x|\,dx}}\]            \[I=\int_{\,0}^{\,\pi /2}{\cos x\,dx}-\int_{\,\pi /2}^{\,\pi }{\cos x\,dx}=[\sin x]_{0}^{\pi /2}-[\sin x]_{\pi /2}^{\pi }\]                                 \[I=\left[ \sin \frac{\pi }{2}-\sin 0 \right]-\left[ \sin \pi -\sin \frac{\pi }{2} \right]\]= 1 + 1 = 2.


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