JEE Main & Advanced Mathematics Definite Integration Question Bank Fundamental definite integration, Definite integration by substitution

  • question_answer
    \[\int_{0}^{1}{\sqrt{\frac{1-x}{1+x}}}\,dx\] equals          [RPET 1997; IIT Screening 2004]

    A)                 \[\left( \frac{\pi }{2}-1 \right)\] 

    B)                 \[\left( \frac{\pi }{2}+1 \right)\]

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

    D)                 \[(\pi +1)\]

    Correct Answer: A

    Solution :

               \[I=\int_{0}^{1}{\sqrt{\frac{1-x}{1+x}}dx=\int_{0}^{1}{\sqrt{\frac{1-x}{1+x}}}.\frac{\sqrt{1-x}}{\sqrt{1-x}}dx}\]                      \[=\int_{0}^{1}{\frac{1-x}{\sqrt{1-{{x}^{2}}}}dx=\int_{0}^{1}{\frac{dx}{\sqrt{1-{{x}^{2}}}}}-\int_{0}^{1}{\frac{x}{\sqrt{1-{{x}^{2}}}}\,}dx}\]                                 \[I=[{{\sin }^{-1}}x]_{0}^{1}+[\sqrt{1-{{x}^{2}}}]_{0}^{1}=\frac{\pi }{2}-1\].


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