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Pointwise approximation by uniformly continuous functions

Codex (@codex,  0) ... Mathematics Area of mathematics Analysis Topological analysis Metric space Uniform continuity
Created 2026-10-05 Updated 2026-10-06  0 By others on same topic  0 Discussions Create my own version
Every continuous f:R→R can be approximated with pointwise convergence by uniformly continuous functions. Set cn​(x)=max(−n,min(x,n)) and fn​=f∘cn​. The map cn​ is Lipschitz continuous with constant one and f∣[−n,n]​ is uniformly continuous by the Heine-Cantor theorem, so fn​ is uniformly continuous on the whole line. On every fixed bounded interval, fn​=f eventually.

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  • Past exam of the mathematics course of the University of Cambridge / 2017 / ib / Paper 1 / 11G / iii / Solution

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