CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2007

  • question_answer
    \[\int{\cos \left\{ 2{{\tan }^{-1}}\sqrt{\frac{1-x}{1+x}} \right\}}dx\]is equal to

    A)  \[\frac{1}{8}({{x}^{2}}-1)+c\]    

    B)  \[\frac{{{x}^{4}}}{4}+c\]

    C)  \[\frac{x}{2}+c\]             

    D)         \[\frac{x}{4}+c\]

    E)  \[\frac{{{x}^{2}}}{2}+c\]

    Correct Answer: E

    Solution :

    Let \[I=\int{\cos \left\{ 2{{\tan }^{-1}}\sqrt{\frac{1-x}{1+x}} \right\}}dx\] Put \[x=cos\theta \] \[\therefore \]  \[I=\int{\cos \left\{ 2{{\tan }^{-1}}\sqrt{\frac{1-\cos \theta }{1+\cos \theta }} \right\}}dx\]                 \[=\int{\cos \left\{ 2{{\tan }^{-1}}\left( \tan \frac{\theta }{2} \right) \right\}}dx\]                 \[=\int{\cos \theta dx=\int{x}\,}dx=\frac{{{x}^{2}}}{2}+c\]


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