J & K CET Engineering J and K - CET Engineering Solved Paper-2012

  • question_answer
    If \[x{{e}^{xy}}=y+{{\sin }^{2}}x,\]then \[\frac{dy}{dx}\]at \[x=0\]is  equal to

    A)  \[0\]

    B)  \[1\]

    C)  \[e\]

    D)  \[-1\]

    Correct Answer: B

    Solution :

    Given,  \[x{{e}^{xy}}=y+{{\sin }^{2}}x\] ?..(i) On differentiating w. r. t .x, we get \[{{e}^{xy}}+x{{e}^{xy}}\left( y+x\frac{dy}{dx} \right)=\frac{dy}{dx}+2\sin x\,\cos x\] ?.(ii) On putting \[x=0,\] in Eq. (i), we get \[0({{e}^{0\times y}})=y+{{\sin }^{2}}(0)\] \[\Rightarrow \] \[0=y+0\Rightarrow y=0\] \[\therefore \] At point \[(0,0),\] from Eq. (ii), \[{{e}^{0}}+0{{e}^{0}}\left( 0+0\frac{dy}{dx} \right)=\frac{dy}{dx}+2\,\sin \,0\,\cos \,0\] \[\Rightarrow \] \[1+0=\frac{dy}{dx}+0\] \[\Rightarrow \] \[\frac{dy}{dx}=1\]


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