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Theorems · Theorem · general topology

closure_compl_singleton

∀ {X : Type u} [inst : TopologicalSpace X] (x : X) [(nhdsWithin x {x}ᶜ).NeBot], closure {x}ᶜ = Set.univ

If x is not an isolated point of a topological space, then the closure of {x}ᶜ is the whole space.

Defined in
Mathlib.Topology.ClusterPt
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Foundations
Depth 76 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes
TopologicalSpaceFilter.NeBot

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