The Hyperbolic (5,4) Tessellation
Pictured are 9 tiles of the Hyperbolic (5,4) tessellation. Each pentagonal tile is regular, congruent with all the others, and tessellates with 4 copies of itself at each vertex. Adjust A and B to explore. As you do so, the pentagons always remain congruent (in the Hyperbolic sense).
What must the angle be at each vertex of the above regular pentagons?