L22A
00:00 Review
01:00 Definition of the degree of a region
03:45 Examples
08:40 The relation between the number of edges and
the degree of a region
12:50 Corollary ( edge-vertex inequality )
22:50 Example
L22B
00:00 Example
02:30 Definition of elementary subdivision
07:00 Definition of homeomorphic graphs
20:30 Examples
22:30 Definition of a subgraph
25:00 Theorem ( Kuratowski's theorem)
32:20 Examples