paperfolding in a square, 3 incircles so that with one's radius = sum of other 2
Source: 2012 Sharygin Geometry Olympiad Final Round 8.3
August 3, 2018
geometryincircleinradiussquare
Problem Statement
A paper square was bent by a line in such way that one vertex came to a side not containing this vertex. Three circles are inscribed into three obtained triangles (see Figure). Prove that one of their radii is equal to the sum of the two remaining ones.(L.Steingarts)