n
nicefa.
Foundational Proof

Proof that the Epigraph of a Convex Function is a Convex Set

Students sometimes struggle to differentiate between the convexity of the function f f itself (where line segments between two points on the graph lie above or on the graph) and the convexity of the *set* epi(f) \text{epi}(f) , which includes all points *above* the graph, not just on it. The inclusion of the α \alpha component is key.
Institutional Reference: Fundamentals of Optimization
View Full Proof →