JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Integration by Substitution

  • question_answer
    \[\int_{{}}^{{}}{\frac{x}{\sqrt{4-{{x}^{4}}}}dx}=\] [Roorkee 1976]

    A)            \[{{\cos }^{-1}}\frac{{{x}^{2}}}{2}\]

    B)            \[\frac{1}{2}{{\cos }^{-1}}\frac{{{x}^{2}}}{2}\]

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

    D)            \[\frac{1}{2}{{\sin }^{-1}}\frac{{{x}^{2}}}{2}\]

    Correct Answer: D

    Solution :

                       \[\int_{{}}^{{}}{\frac{x}{\sqrt{4-{{x}^{4}}}}}\,dx=\int_{{}}^{{}}{\frac{x}{\sqrt{{{2}^{2}}-{{({{x}^{2}})}^{2}}}}}\,dx\]            Putting \[{{x}^{2}}=t\Rightarrow 2x\,dx=dt,\] we get the required integral \[=\frac{1}{2}{{\sin }^{-1}}\frac{{{x}^{2}}}{2}\].


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