Determine whether the vector field \mathrm{F}(x, y)=-y e^{-x y} \mathrm{i}-x e^{-x y} \mathrm{j} is conservative.
With P=-y e^{-x y} and Q=-x e^{-x y}, we find
\frac{\partial P}{\partial y}=x y e^{-x y}-e^{-x y}=\frac{\partial Q}{\partial x} .
The components of \mathrm{F} are continuous and have continuous partial derivatives. Thus (6)
\frac{\partial P}{\partial y}=\frac{\partial Q}{\partial x} (6)
holds throughout the x y-plane, which is a simply connected region. From the converse in Theorem 9.9.4 we can conclude that \mathrm{F} is conservative.