collinearity wanted, 2 squares related
Source: 2023 NZMO - New Zealand Maths Olympiad Round 2 p3
September 2, 2023
geometrycollinear
Problem Statement
Let be a square (vertices labelled in clockwise order). Let be any point on diagonal between and such that . Points and exist such that is a square (vertices labelled in clockwise order) and point lies inside . Let be the point of intersection of lines and (extended if necessary). Prove that , and are colinear