Theorem basis1 21650

Description: Property of a basis. (Contributed by NM, 16-Jul-2006.)

Assertion

Ref	Expression
basis1	⊢ ((𝐵 ∈ TopBases ∧ 𝐶 ∈ 𝐵 ∧ 𝐷 ∈ 𝐵) → (𝐶 ∩ 𝐷) ⊆ ∪ (𝐵 ∩ 𝒫 (𝐶 ∩ 𝐷)))

Proof of Theorem basis1

Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		isbasisg 21647	. . . 4 ⊢ (𝐵 ∈ TopBases → (𝐵 ∈ TopBases ↔ ∀𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 (𝑥 ∩ 𝑦) ⊆ ∪ (𝐵 ∩ 𝒫 (𝑥 ∩ 𝑦))))
2	1	ibi 270	. . 3 ⊢ (𝐵 ∈ TopBases → ∀𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 (𝑥 ∩ 𝑦) ⊆ ∪ (𝐵 ∩ 𝒫 (𝑥 ∩ 𝑦)))
3		ineq1 4109	. . . . 5 ⊢ (𝑥 = 𝐶 → (𝑥 ∩ 𝑦) = (𝐶 ∩ 𝑦))
4	3	pweqd 4513	. . . . . . 7 ⊢ (𝑥 = 𝐶 → 𝒫 (𝑥 ∩ 𝑦) = 𝒫 (𝐶 ∩ 𝑦))
5	4	ineq2d 4117	. . . . . 6 ⊢ (𝑥 = 𝐶 → (𝐵 ∩ 𝒫 (𝑥 ∩ 𝑦)) = (𝐵 ∩ 𝒫 (𝐶 ∩ 𝑦)))
6	5	unieqd 4812	. . . . 5 ⊢ (𝑥 = 𝐶 → ∪ (𝐵 ∩ 𝒫 (𝑥 ∩ 𝑦)) = ∪ (𝐵 ∩ 𝒫 (𝐶 ∩ 𝑦)))
7	3, 6	sseq12d 3925	. . . 4 ⊢ (𝑥 = 𝐶 → ((𝑥 ∩ 𝑦) ⊆ ∪ (𝐵 ∩ 𝒫 (𝑥 ∩ 𝑦)) ↔ (𝐶 ∩ 𝑦) ⊆ ∪ (𝐵 ∩ 𝒫 (𝐶 ∩ 𝑦))))
8		ineq2 4111	. . . . 5 ⊢ (𝑦 = 𝐷 → (𝐶 ∩ 𝑦) = (𝐶 ∩ 𝐷))
9	8	pweqd 4513	. . . . . . 7 ⊢ (𝑦 = 𝐷 → 𝒫 (𝐶 ∩ 𝑦) = 𝒫 (𝐶 ∩ 𝐷))
10	9	ineq2d 4117	. . . . . 6 ⊢ (𝑦 = 𝐷 → (𝐵 ∩ 𝒫 (𝐶 ∩ 𝑦)) = (𝐵 ∩ 𝒫 (𝐶 ∩ 𝐷)))
11	10	unieqd 4812	. . . . 5 ⊢ (𝑦 = 𝐷 → ∪ (𝐵 ∩ 𝒫 (𝐶 ∩ 𝑦)) = ∪ (𝐵 ∩ 𝒫 (𝐶 ∩ 𝐷)))
12	8, 11	sseq12d 3925	. . . 4 ⊢ (𝑦 = 𝐷 → ((𝐶 ∩ 𝑦) ⊆ ∪ (𝐵 ∩ 𝒫 (𝐶 ∩ 𝑦)) ↔ (𝐶 ∩ 𝐷) ⊆ ∪ (𝐵 ∩ 𝒫 (𝐶 ∩ 𝐷))))
13	7, 12	rspc2v 3551	. . 3 ⊢ ((𝐶 ∈ 𝐵 ∧ 𝐷 ∈ 𝐵) → (∀𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 (𝑥 ∩ 𝑦) ⊆ ∪ (𝐵 ∩ 𝒫 (𝑥 ∩ 𝑦)) → (𝐶 ∩ 𝐷) ⊆ ∪ (𝐵 ∩ 𝒫 (𝐶 ∩ 𝐷))))
14	2, 13	syl5com 31	. 2 ⊢ (𝐵 ∈ TopBases → ((𝐶 ∈ 𝐵 ∧ 𝐷 ∈ 𝐵) → (𝐶 ∩ 𝐷) ⊆ ∪ (𝐵 ∩ 𝒫 (𝐶 ∩ 𝐷))))
15	14	3impib 1113	1 ⊢ ((𝐵 ∈ TopBases ∧ 𝐶 ∈ 𝐵 ∧ 𝐷 ∈ 𝐵) → (𝐶 ∩ 𝐷) ⊆ ∪ (𝐵 ∩ 𝒫 (𝐶 ∩ 𝐷)))

Syntax hints:   → wi 4   ∧ wa 399   ∧ w3a 1084   = wceq 1538   ∈ wcel 2111  ∀wral 3070   ∩ cin 3857   ⊆ wss 3858  𝒫 cpw 4494  ∪ cuni 4798  TopBasesctb 21645

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1911  ax-6 1970  ax-7 2015  ax-8 2113  ax-9 2121  ax-10 2142  ax-11 2158  ax-12 2175  ax-ext 2729

This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845  df-3an 1086  df-tru 1541  df-ex 1782  df-nf 1786  df-sb 2070  df-clab 2736  df-cleq 2750  df-clel 2830  df-nfc 2901  df-ral 3075  df-rab 3079  df-v 3411  df-in 3865  df-ss 3875  df-pw 4496  df-uni 4799  df-bases 21646

This theorem is referenced by: (None)