Problem

Source: Tournament of Towns 2020 oral p5 (15 March 2020)

Tags: geometry, 3D geometry, sphere, combinatorial geometry, Tiling, covering, combinatorics



A triangle is given on a sphere of radius $1$, the sides of which are arcs of three different circles of radius $1$ centered in the center of a sphere having less than $\pi$ in length and an area equal to a quarter of the area of the sphere. Prove that four copies of such a triangle can cover the entire sphere. A. Zaslavsky