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

  • question_answer
    \[\int_{{}}^{{}}{\frac{x{{\sin }^{-1}}x}{\sqrt{1-{{x}^{2}}}}\ }dx=\]           [MNR 1978; EAMCET 1982; IIT 1984]

    A)                 \[x-\sqrt{1-{{x}^{2}}}{{\sin }^{-1}}x+c\]

    B)                 \[x+\sqrt{1-{{x}^{2}}}{{\sin }^{-1}}x+c\]

    C)                 \[\sqrt{1-{{x}^{2}}}{{\sin }^{-1}}x-x+c\]

    D)                 None of these

    Correct Answer: A

    Solution :

                    Putting \[{{\sin }^{-1}}x=t\Rightarrow \frac{1}{\sqrt{1-{{x}^{2}}}}\,dx=dt,\] we get                 \[\int_{{}}^{{}}{\frac{x{{\sin }^{-1}}x}{\sqrt{1-{{x}^{2}}}}\,dx=}\int_{{}}^{{}}{t\sin t\,dt=-t\cos t+\sin t+c}\]                                            \[=-{{\sin }^{-1}}x\cos ({{\sin }^{-1}}x)+\sin ({{\sin }^{-1}}x)+c\]                                            \[=x-{{\sin }^{-1}}x\sqrt{1-{{x}^{2}}}+c.\]


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