Chapter 8: Q18E (page 437)
Question: Let v be an element of the convex set S. prove that v is an extreme point of S if an only if the set \(\left\{ {{\bf{x}} \in S:{\bf{x}} \ne {\bf{v}}} \right\}\) is convex.
Short Answer
The point v is an extreme point of S if and only if the set \(\left\{ {{\bf{x}} \in S:\,\,{\bf{x}} \ne {\bf{v}}} \right\}\) is convex.