CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2009

  • question_answer
    The solution of \[\cos y\frac{dy}{dx}={{e}^{x+\sin y}}+{{x}^{2}}{{e}^{\sin y}}\]is

    A)  \[{{e}^{x}}-{{e}^{-\sin y}}+\frac{{{x}^{3}}}{3}=c\]

    B)  \[{{e}^{-x}}-{{e}^{-\sin y}}+\frac{{{x}^{3}}}{3}=c\]

    C)  \[{{e}^{x}}+{{e}^{-\sin y}}+\frac{{{x}^{3}}}{3}=c\]

    D)  \[{{e}^{x}}-{{e}^{\sin y}}-\frac{{{x}^{3}}}{3}=c\]

    E)  \[{{e}^{x}}-{{e}^{\sin y}}+\frac{{{x}^{3}}}{3}=c\]

    Correct Answer: C

    Solution :

    Given, \[\cos y\frac{dy}{dx}={{e}^{x+\sin y}}+{{x}^{2}}{{e}^{\sin y}}\] \[\Rightarrow \]               \[\cos y\frac{dy}{dx}={{e}^{\sin y}}({{e}^{x}}+{{x}^{2}})dx\] \[\Rightarrow \]               \[\int{\frac{\cos y}{{{e}^{\sin y}}}dy}=\int{({{e}^{x}}+{{x}^{2}})dx}\] Put \[\sin y=t\]in \[LHS\Rightarrow \cos ydy=dt\] \[\therefore \]  \[\int{\frac{dt}{{{e}^{t}}}}=\int{({{e}^{x}}+{{x}^{2}})}dx\] \[\Rightarrow \]               \[-{{e}^{-t}}={{e}^{x}}+\frac{{{x}^{3}}}{3}-c\] \[\Rightarrow \]               \[{{e}^{x}}+{{e}^{-\sin y}}+\frac{{{x}^{3}}}{3}=c\]


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