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

  • question_answer
    The correct evaluation of \[\int_{0}^{\pi /2}{\left| \,\sin \left( x-\frac{\pi }{4} \right)\, \right|\,dx}\] is [MP PET 1993]

    A)                 \[2+\sqrt{2}\]   

    B)                 \[2-\sqrt{2}\]

    C)                 \[-2+\sqrt{2}\] 

    D)                 0

    Correct Answer: B

    Solution :

               Let \[I=\int_{0}^{\pi /2}{\left| \sin \left( x-\frac{\pi }{4} \right)\, \right|}\,dx\]                    \[x-\frac{\pi }{4}\]is ?ve when \[x\le \frac{\pi }{4}\]and +ve when \[x>\frac{\pi }{4}\]                                 \[=-\int_{0}^{\pi /4}{\sin \left( x-\frac{\pi }{4} \right)dx+\int_{\pi /4}^{\pi /2}{\sin \left( x-\frac{\pi }{4} \right)dx}}\]\[=2-\sqrt{2}\].


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