JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Mock Test - Integrals

  • question_answer
    Given \[\int\limits_{0}^{\pi /2}{\frac{dx}{1+\sin x+\cos x}=\log \,2.}\] Then the value of the definite integral \[\int\limits_{0}^{\pi /2}{\frac{\sin x}{1+\sin x+\cos x}dx}\]is equal to

    A) \[\frac{1}{2}\log 2\]       

    B) \[\frac{\pi }{2}-\log 2\]

    C) \[\frac{\pi }{4}-\frac{1}{2}\log 2\]          

    D) \[\frac{\pi }{2}+\log 2\]

    Correct Answer: C

    Solution :

    [c] \[I=\int\limits_{0}^{\pi /2}{\frac{\sin xdx}{1+\sin x+\cos x}}\] \[=\int\limits_{0}^{\pi /2}{\frac{\cos xdx}{1+\sin x+\cos x}}\] Or \[2I=\int\limits_{0}^{\pi /2}{\frac{\sin x+\cos x+1-1}{\sin x+\cos x+1}dx}\] \[2I=\frac{\pi }{2}-\log 2\] Or \[I=\frac{\pi }{4}-\frac{1}{2}\log 2\]


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