Topic: Topology (Undergraduate)

The Deleted Tychonoff Plank

The Coordinatewise Continuity Theorem

The Compact-to-Hausdorff Homeomorphism Argument

The Complete-Metric Baire Theorem by Nested Balls

The Cofinite Topology

The Compact-Open Subbasis

The Cocountable Topology: Lindelof But Not Second Countable

The Coarsest Topology Making Projections Continuous

The Closure of a Connected Set Is Connected

The Closed-Set Test for Continuity