CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2008

  • question_answer
    \[\int{\frac{\sin x\,\cos x}{\sqrt{1-{{\sin }^{4}}x}}}dx\] is equal to

    A)  \[\frac{1}{2}{{\sin }^{-1}}({{\sin }^{2}}x)+C\]

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

    C)  \[{{\tan }^{-1}}({{\sin }^{2}}x)+C\]

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

    Correct Answer: A

    Solution :

    Let    \[I=\int{\frac{\sin x\cos x}{\sqrt{1-{{\sin }^{4}}x}}dx}\] Put \[{{\sin }^{2}}x=t\Rightarrow 2\sin \,x\,\cos \,x\,dx=dt\] \[\therefore \]  \[I=\int{\frac{dt}{2\sqrt{1-{{t}^{2}}}}}\]                 \[=\frac{1}{2}{{\sin }^{-1}}t+C\]                 \[=\frac{1}{2}{{\sin }^{-1}}({{\sin }^{2}}x)+C\]


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