AD,CD \cap [ABC] is empty
Source: Saint Petersburg olympiad 2024, 11.5
September 22, 2024
geometrycombinatorial geometry
Problem Statement
There are points of general position marked on the plane (i.e. no three lie on the same straight line). Prove that it is possible to select three marked points so that for any point of the remaining marked points, the lines and would not contain points lying inside the triangle .