CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2003

  • question_answer
    Solution of the differential equation \[\tan y.{{\sec }^{2}}xdx+\tan x.{{\sec }^{2}}ydy=0\] is:

    A)  \[tan\text{ }x+tan\text{ }y=k\]

    B)  \[tan\text{ }x-tan\text{ }y=k\]

    C)  \[(tan\text{ }x/tan\text{ }y)=k\]

    D)  \[tan\text{ }x.tan\text{ }y=k\]

    E)  None of the above

    Correct Answer: D

    Solution :

    \[\tan y{{\sec }^{2}}xdx+\tan x{{\sec }^{2}}ydy=0\] \[\Rightarrow \]               \[\int{\frac{{{\sec }^{2}}x}{\tan x}}dx+\int{\frac{{{\sec }^{2}}y}{\tan y}}dy=0\] \[\Rightarrow \]               \[\log \tan x+\log \tan y=\log k\] \[\Rightarrow \]               \[\tan x\tan y=k\]


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