Back

Triangle dissection, no shared edges: https://math.stackexchange.com/questions/1819928/triangle-dissection-no-shared-edges
(the intended target of a recent broken link from mathpuzzle.com)

The question is how to divide a triangle into smaller triangles, no two sharing a whole edge, but the solutions shown also have no separating triangles and a straight angle at each interior vertex. Double-counting angles and combining with Euler shows that, with these conditions, $F=V-1$. Do all internally-4-connected planar graphs with $F=V-1$ work?