JEE Main & Advanced Mathematics Definite Integration Question Bank Fundamental definite integration, Definite integration by substitution

  • question_answer
    \[\int_{0}^{1/\sqrt{2}}{\frac{{{\sin }^{-1}}x}{{{(1-{{x}^{2}})}^{3/2}}}dx=}\]                                            [Roorkee 1984]

    A)                 \[\frac{\pi }{4}+\frac{1}{2}\log 2\]           

    B)                 \[\frac{\pi }{4}-\frac{1}{2}\log 2\]

    C)                 \[\frac{\pi }{2}+\log 2\]

    D)                 \[\frac{\pi }{2}-\log 2\]

    Correct Answer: B

    Solution :

               \[I=\int_{0}^{1/\sqrt{2}}{\frac{{{\sin }^{-1}}x}{{{(1-{{x}^{2}})}^{3/2}}}}dx\]            Put \[{{\sin }^{-1}}x=t\Rightarrow \frac{1}{\sqrt{1-{{x}^{2}}}}dx=dt\]and \[x=\sin t\]            Also \[t=0\]to \[\frac{\pi }{4}\]as \[x=0\]to \[\frac{1}{\sqrt{2}}\]                 \[\Rightarrow I=\int_{0}^{\pi /4}{t.{{\sec }^{2}}t\,dt=\frac{\pi }{4}-\frac{1}{2}\log 2}\].


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