8 problems.
- A limit point of a union is a limit point of one of the sets
- A compact topology on \(\ZZ\) from cofinite sets and sets omitting \(0\)
- Joining a connected set to one side of a separation of its complement
- Metacompactness is a homeomorphism invariant, and an included-point topology that is not metacompact
- Cell structure and fundamental group of a torus and sphere with two torus points identified to a sphere point
- The fundamental group of the Klein bottle is nonabelian, via covering spaces
- Simplicial homology of \(S^2\) with three points identified
- Unicoherence of \(S^n\) for \(n\ge 2\) via Mayer–Vietoris