56
[19D] A closed convex set \(Aβ {\mathbb {R}}^ n\) is said strictly convex if, for every \(x,yβ A\) with \(xβ y\) and every \(tβ (0,1)\) you have
\[ (tx+(1-t)y)β {{A}^\circ }\quad . \]
[19D] A closed convex set \(Aβ {\mathbb {R}}^ n\) is said strictly convex if, for every \(x,yβ A\) with \(xβ y\) and every \(tβ (0,1)\) you have