Pro k�ivku $\varphi : t \to \varphi (t)$, $t \in [0,1]$
vezm�me k�ivku $\psi : t \to \psi (t)$, $t \in [0,1]$
definovanou p�edpisem $\psi (t) := \varphi (1-t)$ .
Doka�te, �e
$$
\int \! \BBb F {d \vec \varphi}  = -
\int \! \BBb F {d \vec \psi} \quad .
$$