Topic: Topology (Undergraduate)

The Closed-Set Form of Tychonoff’s Theorem

The Closed-Set Shrinking Lemma in Normal Spaces

The Closed-Cover Pasting Lemma

The Closed-Cover Consequence of the Baire Theorem

The Classification Theorem for Compact Surfaces

The Circle as the Real Line Modulo Integers

The Circle’s Relative Topology in the Plane

The Cantor-Schroeder-Bernstein Theorem

The Cantor Set As A Perfect Nowhere-Dense Compactum

The Bounded Tietze Extension Theorem