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Theorem

Tietze Extension Theorem

Topology

The Tietze Extension Theorem states that a continuous real-valued function defined on a closed subset of a normal topological space can always be extended to a continuous function on the whole space. Named for Heinrich Tietze, building on earlier work by Henri Lebesgue, it is a fundamental tool for constructing continuous functions with prescribed behavior on a subspace.

Facts
Statement
The Tietze extension theorem states that any real valued continuous function defined on a closed subset of a normal topological space can be extended to a continuous function on the whole space, preserving boundedness if the original function was bounded. 1
Classification
Statement Form
Existence Theorem 1
Connections

Has Statement Form

Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.

In Branch

Proved By

Source Tietze Extension Theorem (Wikipedia)
Source Tietze Extension Theorem (Wikipedia)
Sources
1. Tietze Extension Theorem (Wikipedia)
Wikimedia Foundation
  • lead section, first paragraph
    In topology, the Tietze extension theorem (also known as the Tietze-Urysohn-Brouwer extension theorem or Urysohn-Brouwer lemma) states that any real-valued, continuous function on a closed subset of a normal topological space can be extended to the entire space, preserving boundedness if necessary.
  • Proved By: Heinrich Tietze, Lead paragraph
    In topology, the Tietze extension theorem (also known as the Tietze-Urysohn-Brouwer extension theorem or Urysohn-Brouwer lemma) states that any
  • Proved By: Pavel Urysohn, Lead paragraph
    In topology, the Tietze extension theorem (also known as the Tietze-Urysohn-Brouwer extension theorem or Urysohn-Brouwer lemma) states that any real-valued, continuous function on a closed subset
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