exists_countable_union_perfect_of_isClosed

∀ {α : Type u_1} [inst : TopologicalSpace α] {C : Set α} [SecondCountableTopology α],
  IsClosed C → ∃ V D, V.Countable ∧ Perfect D ∧ C = V ∪ D

The Cantor-Bendixson Theorem: Any closed subset of a second countable space can be written as the union of a countable set and a perfect set.

Defined in: Mathlib.Topology.Perfect
Cited by: 1 results in Mathlib
Foundations: Depth 78 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes: TopologicalSpace SecondCountableTopology

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