CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2008

  • question_answer
    If\[y={{\tan }^{-1}}\left( \frac{4x}{1+5{{x}^{2}}} \right)+{{\tan }^{-1}}\left( \frac{2+3x}{3-2x} \right),\]then\[\frac{dy}{dx}\]is equal to

    A)  \[\frac{5}{1+25{{x}^{2}}}\]         

    B)         \[\frac{1}{1+25{{x}^{2}}}\]

    C)  \[0\]                    

    D)         \[\frac{5}{1-25{{x}^{2}}}\]

    E)  None of these

    Correct Answer: A

    Solution :

    Given, \[y={{\tan }^{-1}}\left( \frac{4x}{1+5{{x}^{2}}} \right)+{{\tan }^{-1}}\left( \frac{2+3x}{3-2x} \right)\] Or \[y={{\tan }^{-1}}\left( \frac{5x-x}{1+5{{x}^{2}}} \right)+{{\tan }^{-1}}\left( \frac{\frac{2}{3}+x}{1-\frac{2}{3}x} \right)\] \[\Rightarrow \]\[y={{\tan }^{-1}}(5x)+{{\tan }^{-1}}(x)\]                                 \[+{{\tan }^{-1}}\left( \frac{2}{3} \right)+{{\tan }^{-1}}(x)\] \[\Rightarrow \]\[y={{\tan }^{-1}}(5x)+{{\tan }^{-1}}\left( \frac{2}{3} \right)\] On differentiating w.r.t.\[x,\]we get \[\frac{dy}{dx}=\frac{5}{1+{{(5x)}^{2}}}=\frac{5}{1+25{{x}^{2}}}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner