1978 points on plane
Source: Netherlands - Dutch NMO 1978 p3
January 28, 2023
pointscombinatoricscombinatorial geometry
Problem Statement
There are points in the flat plane. Each point has a circular disk with that point as its center and the radius is the distance to a fixed point. Prove that there are five of these circular disks, which together cover all points (circular disk means: the circle and its inner area).