Topic: Topology (Undergraduate)

Worked Applications of the Lifting Criterion

Why The Sorgenfrey Line Is Separable But Not Second Countable

Why The One-Point Extension Is Compact

Why The Long Line Is Not Metrizable

Why the Circle Cannot Embed in the Line

Why the Cofinite Topology Satisfies the Axioms

Why Path-Connected Spaces Are Connected

Why Paths Cannot Join the Sine Curve Branches

Why Metric-Open Sets Form a Topology

Why Interior Does Not Preserve Unions