Kakutani fixed-point theorem
= Kakutani fixed-point theorem
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A nonempty <compact convex set> $K$ in a finite-dimensional space and an <upper hemicontinuous> <set-valued mapping> $F:K\rightrightarrows K$ with nonempty closed <convex> values admit $x\in F(x)$. A closed graph suffices when the whole output space is <compact>.