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

  • question_answer
    The solution of the equation \[{{\sin }^{-1}}\left( \frac{dy}{dx} \right)=x+y\]is

    A)                 \[\tan (x+y)+\sec (x+y)=x+c\]          

    B)                 \[\tan (x+y)-\sec (x+y)=x+c\]

    C)                 \[\tan (x+y)+\sec (x+y)+x+c=0\]

    D)                 None of these

    Correct Answer: B

    Solution :

                       Here \[\frac{dy}{dx}=\sin (x+y)\]         Now put \[\log (1+y)=x+\frac{{{x}^{2}}}{2}+\log c\]and \[\frac{dy}{dx}=\frac{dv}{dx}-1\]         Therefore \[\frac{dy}{dx}=\sin (x+y)\]reduces to \[\frac{dv}{1+\sin v}=dx\]         Now on integrating both the sides, we get                 \[\tan v-\sec v=x+c\] or \[\tan (x+y)-\sec (x+y)=x+c\].


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