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

  • question_answer
    \[\int_{{}}^{{}}{\frac{1}{{{\cos }^{-1}}x.\sqrt{1-{{x}^{2}}}}dx=}\]

    A)            \[\log ({{\cos }^{-1}}x)+c\]

    B)            \[-\log ({{\cos }^{-1}}x)+c\]

    C)            \[-\frac{1}{2{{({{\cos }^{-1}}x)}^{2}}}+c\]

    D)            None of these

    Correct Answer: B

    Solution :

                       Put \[{{\cos }^{-1}}x=t\Rightarrow -\frac{1}{\sqrt{1-{{x}^{2}}}}\,dx=dt,\] then            \[\int_{{}}^{{}}{\frac{1}{{{\cos }^{-1}}\sqrt{1-{{x}^{2}}}}\,dx=-\int_{{}}^{{}}{\frac{1}{t}\,dt}}=-\log t+c=\log \frac{1}{t}+c\]                                                                   \[=-\log ({{\cos }^{-1}}x)+c.\]


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