JEE Main & Advanced Mathematics Differential Equations Question Bank Variable Separable type differential equations

  • question_answer
    Solution of the differential equation \[\frac{dy}{dx}\tan y=\sin (x+y)+\sin (x-y)\] is  [Kerala (Engg.) 2005]

    A)                 \[\sec y+2\cos x=c\]             

    B)                 \[\sec y-2\cos x=c\]

    C)                 \[\cos y-2\sin x=c\]               

    D)                 \[\tan y-2\sec y=c\]

    E)                 \[\sec y+2\sin x=c\]

    Correct Answer: A

    Solution :

               \[\frac{dy}{dx}\tan y=\sin (x+y)+\sin (x-y)\]                    \[\frac{dy}{dx}(\tan y)=2\sin x\cos y\] Þ \[\frac{\sin y}{{{\cos }^{2}}y}dy=2\sin xdx\]                    Þ \[\int{\frac{\sin y}{{{\cos }^{2}}y}}dy=2\int{\sin xdx}\] Þ \[\frac{1}{\cos y}=-2\cos x+c\]                                 \ \[\sec y+2\cos x=c\].


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