CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    \[{{\tan }^{-1}}x+{{\tan }^{-1}}y=c\]is general solution of the differential equation:

    A)  \[\frac{dy}{dx}=\frac{1+{{y}^{2}}}{1+{{x}^{2}}}\]             

    B)         \[\frac{dy}{dx}=\frac{1+{{x}^{2}}}{1+{{y}^{2}}}\]

    C)  \[(1+{{x}^{2}})dy+(1+{{y}^{2}})dx=0\]

    D)  \[\frac{dy}{dx}=\frac{1-{{y}^{2}}}{1-{{x}^{2}}}\]

    E)  \[(1-{{x}^{2}})dx+(1-y)dy=0\]

    Correct Answer: C

    Solution :

    \[{{\tan }^{-1}}x+{{\tan }^{-1}}y=c\] On differentiating w.r.t\[x\]we get \[\frac{1}{1+{{x}^{2}}}+\frac{1}{1+{{y}^{2}}}\frac{dy}{dx}=0\] \[\Rightarrow \]               \[(1+{{x}^{2}})dy(1+{{y}^{2}})dx=0\]


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