Science, Maths & Technology
Surfaces
...DE}, faces {1, 2, 3, 4}. Faces 1 and 2 meet at the edge AE and at vertices A and E. Faces 1 and 3 meet at vertex E only. Faces 1 and 4 meet at edge DE and at vertices D and E. Face 3 has 3 edges (BC, BE, CE) and 3 vertices (B, C and E). We noted earlier that the endpoints of an edge may coincide. This means that an edge can meet itself, as is illustrated by the circular...