CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2003

  • question_answer
    \[\int_{0}^{2\pi }{(\sin x+|\sin x|dx}\] is equal to :

    A)  4                                            

    B)  0

    C)  1                                            

    D)  8

    Correct Answer: A

    Solution :

    We have \[\int_{0}^{2\pi }{(\sin x+|\sin x|\,dx}\] \[=\int_{0}^{2\pi }{(\sin x+|\sin x|\,dx}+\int_{\pi }^{2\pi }{{}}\]                                                 \[(\sin x+|\sin x|)dx\]                    \[\left[ Using\,\int_{0}^{2a}{f(x)}\,dx=\int_{0}^{a}{f(x)\,dx+}\int_{a}^{2a}{f(x)\,dx} \right]\] \[=\int_{0}^{\pi }{(\sin x+\sin x)dx+\int_{\pi }^{2\pi }{(\sin x-\sin x)dx}}\] \[=\int_{0}^{\pi }{2\sin x\,dx+0}\] [\[|\sin x|\] is \[-ve\] in \[\pi \to 2\pi \] and \[(\sin x)\] is \[+ve\]in \[0\to \pi \]]                 \[=2\,\int_{0}^{\pi }{\sin x\,dx}\]                 \[=2\,[-\cos x]_{0}^{\pi }\]                 \[=-2\,(\cos \pi -\cos \,0)\]                 \[=-2\,(-1-1)\]                 \[=4\]


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