= Variational inequality
{title2=$F(x^*)\cdot(x-x^*)\geq0\quad(x\in K)$}
For a feasible set $K$ and a vector field $F$, a <variational inequality> asks for $x^*\in K$ satisfying the displayed inequality for every feasible $x$. If $K$ is convex and $F$ is the gradient of a differentiable <convex function>, it is the necessary and sufficient first-order condition for minimizing that function. It also describes <Wardrop equilibria> when no scalar objective has the route-cost vector as its gradient.
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