9.5

Part of 2001 All-Russian Olympiad Regional Round

Problems(1)

2 points in a convex pentagon - All-Russian MO 2001 Regional (R4) 9.5

Source:

Two points are selected in a convex pentagon. Prove that you can choose a quadrilateral with vertices at the vertices of a pentagon so that both selected points fall into it.

geometrycombinatoricscombinatorial geometry