BCECE Engineering BCECE Engineering Solved Paper-2012

  • question_answer
    \[\int_{{}}^{{}}{\frac{2x{{\tan }^{-1}}{{x}^{2}}}{1+{{x}^{4}}}}dx\]

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

    B)         \[\frac{1}{2}{{[{{\tan }^{-1}}{{x}^{2}}]}^{2}}+C\]              

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

    D)         None of above

    Correct Answer: B

    Solution :

    Put \[t={{\tan }^{-1}}{{x}^{2}}\] \[\Rightarrow \]               \[dt=\frac{1}{1+{{x}^{4}}}2xdx,\]then \[\int_{{}}^{{}}{\frac{2x{{\tan }^{-1}}{{x}^{2}}}{1+{{x}^{4}}}}dx=\int_{{}}^{{}}{fdt=\frac{{{t}^{2}}}{2}+C}\] \[=\frac{1}{2}{{({{\tan }^{-1}}{{x}^{2}})}^{2}}+C\]


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