A simple proof of Pach's extremal theorem for convex polygons

A simple proof is given that the minimum-area triangle inscribed in a convex polygon has two sides which are edges of the polygon.

[1]  David P. Dobkin,et al.  On a general method for maximizing and minimizing among certain geometric problems , 1979, 20th Annual Symposium on Foundations of Computer Science (sfcs 1979).

[2]  János Pach.  On an isoperimetric problem , 1978 .