CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    \[\int{\sqrt{\frac{1-x}{1+x}}}dx\]is equal to

    A)  \[{{\sin }^{-1}}x+\sqrt{1-{{x}^{2}}}+C\]

    B)  \[{{\sin }^{-1}}x-2\sqrt{1-{{x}^{2}}}+C\]

    C)  \[2{{\sin }^{-1}}x-\sqrt{1-{{x}^{2}}}+C\]

    D)  \[{{\sin }^{-1}}x-\sqrt{1-{{x}^{2}}}+C\]

    E)  \[-{{\cos }^{-1}}x-\sqrt{1-{{x}^{2}}}+C\]

    Correct Answer: A

    Solution :

    \[\int{\sqrt{\frac{1-x}{1+x}}}dx\int{\sqrt{\frac{(1-x)(1-x)}{(1+x)(1-x)}}}dx\] After rationalizing                 \[=\int{\frac{(1-x)}{\sqrt{1-{{x}^{2}}}}}dx\]                 \[=\int{\frac{dx}{\sqrt{1-{{x}^{2}}}}-\frac{1}{2}\int{\frac{2x}{\sqrt{1-{{x}^{2}}}}}}dx\]                 \[={{\sin }^{-1}}x-\frac{1}{2}(-2\sqrt{1-{{x}^{2}}})+C\]                 \[={{\sin }^{-1}}x+\sqrt{1+{{x}^{2}}}+C\]


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