Nech� $F(x,y) = (y,2x)$. 
Spo�t�te $\int F\ d\varphi$ a $\int F\ d\psi$, pro 
$\varphi(t) = (1+t,1+3t)$, $t\in <0,1>$ a
$\psi(t) = (t,t^2)$,$t\in <1,2>$.
Je vektorov� pole $F$ konzervativn�?
