JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2013

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

    A)  \[\log |x-\sqrt{{{x}^{2}}-1}|-{{\tan }^{-1}}x+C\]

    B)  \[\log |x+\sqrt{{{x}^{2}}-1}|-{{\tan }^{-1}}x+C\]

    C)  \[\log |x-\sqrt{{{x}^{2}}-1}|-{{\sec }^{-1}}x+C\]

    D)  \[\log |x+\sqrt{{{x}^{2}}-1}|-{{\sec }^{-1}}x+C\]

    Correct Answer: D

    Solution :

                     Let \[I=\int{\frac{\sqrt{x-1}}{x\sqrt{x+1}}}dx=\int{\frac{x-1}{x\sqrt{{{x}^{2}}-1}}}dx\] \[=\int{\frac{dx}{\sqrt{{{x}^{2}}-1}}-\int{\frac{dx}{x\sqrt{{{x}^{2}}-1}}}}\] \[=\log |x+\sqrt{{{x}^{2}}+1}|-{{\sec }^{-1}}x+C\]


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