JCECE Engineering JCECE Engineering Solved Paper-2014

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

    A) \[0\]                                     

    B) \[2\]

    C)  \[1\]                                    

    D)  \[-1\]

    Correct Answer: B

    Solution :

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


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