CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    \[\int{\frac{x{{\sin }^{-1}}x}{\sqrt{1-{{x}^{2}}}}}dx\]is equal to

    A)  \[x-{{\sin }^{-1}}x+C\]

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

    C)  \[x+{{\sin }^{-1}}x+C\]

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

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

    Correct Answer: B

    Solution :

    \[\int{\frac{x{{\sin }^{-1}}x}{\sqrt{1-{{x}^{2}}}}}dx\] Put         \[t={{\sin }^{-1}}x\] \[\Rightarrow \]               \[x=\sin t\]                 \[dt=\frac{dx}{\sqrt{1-{{x}^{2}}}}\] \[\Rightarrow \]               \[\int{x\,.\,tdt}\]                 \[\int{\underset{I}{\mathop{t}}\,.\underset{II}{\mathop{\sin }}\,t\,dt}\]                 \[=[t(-\cos t)-\int{1.(-\cos t)dt]}\]                 \[=-t\cos t+\sin t+C\]                 \[=-t\sqrt{1-{{\sin }^{2}}t}+\sin t+C\]                 \[=-\sqrt{1-{{x}^{2}}}.{{\sin }^{-1}}x+x+C\]                 \[=x-\sqrt{1-{{x}^{2}}}.{{\sin }^{-1}}x+C\]


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