Figure 8
v is a vertex of a triangle (shown in black) of level k. At v there is a small hexagon and its stripe allows for only two things to happen: either one of the edges of the triangle extends through v, in which case it is an edge from a larger triangle, or there is an edge passing through v that is parallel to the opposite edge of the triangle. In the latter case we use (i) of proposition 4.1 to place down the two opposite pairs of triangles of adjoining triangles, shown in green (the adjacent edges are actually coincident edges of course). Then we see that the edge through v must actually be an edge that includes both the top edges of the green triangles: thus again a larger triangle. |