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

  • question_answer
    The general solution of the equation \[({{e}^{y}}+1)\cos xdx+{{e}^{y}}\sin xdy=0\] is    [SCRA 1986]

    A)                 \[({{e}^{y}}+1)\cos x=c\]

    B)                 \[({{e}^{y}}-1)\sin x=c\]

    C)                 \[({{e}^{y}}+1)\sin x=c\]

    D)                 None of these

    Correct Answer: C

    Solution :

                       \[({{e}^{y}}+1)\cos xdx+{{e}^{y}}\sin xdy=0\]                    Þ \[\frac{{{e}^{y}}dy}{{{e}^{y}}+1}+\frac{\cos x}{\sin x}dx=0\]                    On integrating both the functions, we get                                 \[\log ({{e}^{y}}+1)+\log (\sin x)=\log c\] Þ\[({{e}^{y}}+1)\sin x=c\].


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