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

  • question_answer
    \[\int_{1/4}^{1/2}{\frac{dx}{\sqrt{x-{{x}^{2}}}}=}\]                                          [SCRA 1986]

    A)                 \[\pi \] 

    B)                 \[\frac{\pi }{2}\]

    C)                 \[\frac{\pi }{3}\]              

    D)                 \[\frac{\pi }{6}\]

    Correct Answer: D

    Solution :

               \[\int_{1/4}^{1/2}{\frac{dx}{\sqrt{x-{{x}^{2}}}}=\int_{1/4}^{1/2}{\frac{dx}{\sqrt{{{\left( \frac{1}{2} \right)}^{2}}-{{\left( x-\frac{1}{2} \right)}^{2}}}}}}=\left[ {{\sin }^{-1}}\left( \frac{\frac{2x-1}{2}}{1/2} \right) \right]_{1/4}^{1/2}\]                                                    \[=[{{\sin }^{-1}}(2x-1)]_{1/6}^{1/2}=\pi /6\].


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