any set of n points in plane has a free subset of at least \sqrt{n} points
Source: Indian Postal Coaching 2008 set 4 p6
May 25, 2020
combinatoricscombinatorial geometryEquilateralpoints
Problem Statement
A set of points in the plane is called free if no three points of the set are the vertices of an equilateral triangle. Prove that any set of points in the plane has a free subset of at least points