JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2008

  • question_answer
        \[\int{\frac{dx}{x\sqrt{{{x}^{6}}-16}}}\]is equal to

    A)  \[\frac{1}{3}{{\sec }^{-1}}\left( \frac{{{x}^{3}}}{4} \right)+c\]     

    B)  \[{{\cos }^{-1}}\left( \frac{{{x}^{3}}}{4} \right)+c\]

    C)  \[\frac{1}{12}{{\sec }^{-1}}\left( \frac{{{x}^{3}}}{4} \right)+c\]   

    D)  \[{{\sec }^{-1}}\left( \frac{{{x}^{3}}}{4} \right)+c\]

    Correct Answer: C

    Solution :

                    Let \[I=\int{\frac{dx}{x\sqrt{{{x}^{6}}-16}}}\] \[=\frac{1}{3}\int{\frac{3{{x}^{2}}}{{{x}^{3}}\sqrt{{{({{x}^{3}})}^{2}}-{{4}^{2}}}}}dx\] Put            \[{{x}^{3}}=t\] \[\Rightarrow \]               \[3{{x}^{2}}dx=dt\] \[\therefore \]  \[I=\frac{1}{3}\int{\frac{dt}{t\sqrt{{{t}^{2}}-{{4}^{2}}}}}\]                 \[=\frac{1}{3\times 4}{{\sec }^{-1}}\left( \frac{t}{4} \right)+c\]                 \[=\frac{1}{12}{{\sec }^{-1}}\left( \frac{{{x}^{3}}}{4} \right)+c\]


You need to login to perform this action.
You will be redirected in 3 sec spinner