What is a closed set ?
8:11
Can a ball be a sphere?
23:48
Taste of topology: Open Sets
22:38
Compactness
11:48
All About Closed Sets and Closures of Sets (and Clopen Sets) | Real Analysis
14:24
Topology Definitions: Closure, Boundary, Interior
27:03
Connectedness
19:32
Properties of Compactness
12:35