CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2005

  • question_answer
    The value of\[\frac{d}{dx}\left[ {{\tan }^{-1}}\left( \frac{\sqrt{x}(3-x)}{1-3x} \right) \right]\]

    A)  \[\frac{1}{2(1+x)\sqrt{x}}\]       

    B)         \[\frac{3}{(1+x)\sqrt{x}}\]

    C)  \[\frac{2}{(1+x)\sqrt{x}}\]          

    D)         \[\frac{3}{2(1-x)\sqrt{x}}\]

    E)  \[\frac{3}{2(1+x)\sqrt{x}}\]

    Correct Answer: E

    Solution :

    Let \[y={{\tan }^{-1}}\left\{ \frac{3\sqrt{x}-{{x}^{3/2}}}{1-3x} \right\}\] Again let \[\sqrt{x}=\tan t\] \[\therefore \]\[y={{\tan }^{-1}}\left\{ \frac{3\tan t-{{\tan }^{3}}t}{1-3{{\tan }^{2}}t} \right\}={{\tan }^{-1}}(\tan 3t)\] \[\Rightarrow \]               \[y=3{{\tan }^{-1}}\sqrt{x}\] On differentiating, we get \[\frac{dy}{dx}=\frac{3}{1+x}.\frac{1}{2\sqrt{x}}=\frac{3}{2(1+x)\sqrt{x}}\]


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