JEE Main & Advanced Sample Paper JEE Main Sample Paper-37

  • question_answer
    The value of the definite integral\[\int\limits_{0}^{3\pi /4}{[(1+x)\sin x+(1-x)\cos x]dx}\]is-

    A) \[2\tan \frac{3\pi }{8}\]                      

    B) \[2\tan \frac{\pi }{4}\]

    C) \[2\tan \frac{\pi }{8}\]            

    D) \[0\]

    Correct Answer: A

    Solution :

    \[I=\int\limits_{0}^{3\pi /4}{(\sin x+\cos x)dx}+\int\limits_{0}^{3\pi /4}{\underbrace{x}_{I}}\underbrace{(\sin x-\cos x)}_{II}dx\] \[=\int\limits_{0}^{3\pi /4}{(\sin x+\cos x)dx}+\underbrace{x(-\cos x-\sin x)|_{0}^{3\pi /4}}_{zero}\] \[+\int\limits_{0}^{3\pi /4}{(\sin x+\cos x)}dx\]


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