Metamath Proof Explorer


Theorem regr1

Description: A regular space is R_1, which means that any two topologically distinct points can be separated by neighborhoods. (Contributed by Mario Carneiro, 25-Aug-2015)

Ref Expression
Assertion regr1 ⊢ J ∈ Reg → KQ ⁡ J ∈ Haus

Proof

Step Hyp Ref Expression
1 regtop ⊢ J ∈ Reg → J ∈ Top
2 toptopon2 ⊢ J ∈ Top ↔ J ∈ TopOn ⁡ ⋃ J
3 1 2 sylib ⊢ J ∈ Reg → J ∈ TopOn ⁡ ⋃ J
4 eqid ⊢ x ∈ ⋃ J ⟼ y ∈ J | x ∈ y = x ∈ ⋃ J ⟼ y ∈ J | x ∈ y
5 4 regr1lem2 ⊢ J ∈ TopOn ⁡ ⋃ J ∧ J ∈ Reg → KQ ⁡ J ∈ Haus
6 3 5 mpancom ⊢ J ∈ Reg → KQ ⁡ J ∈ Haus