Theorem bj-0int 38022

Description: If 𝐴 is a collection of subsets of 𝑋, like a Moore collection or a topology, two equivalent ways to say that arbitrary intersections of elements of 𝐴 relative to 𝑋 belong to some class 𝐵: the LHS singles out the empty intersection (the empty intersection relative to 𝑋 is 𝑋 and the intersection of a nonempty family of subsets of 𝑋 is included in 𝑋, so there is no need to intersect it with 𝑋). In typical applications, 𝐵 is 𝐴 itself. (Contributed by BJ, 7-Dec-2021.)

Assertion

Ref	Expression
bj-0int	⊢ (𝐴 ⊆ 𝒫 𝑋 → ((𝑋 ∈ 𝐵 ∧ ∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})∩ 𝑥 ∈ 𝐵) ↔ ∀𝑥 ∈ 𝒫 𝐴(𝑋 ∩ ∩ 𝑥) ∈ 𝐵))

Distinct variable groups:   𝑥,𝐴   𝑥,𝐵   𝑥,𝑋

Proof of Theorem bj-0int

Step	Hyp	Ref	Expression
1		ssv 3955	. . . . . . . . 9 ⊢ 𝑋 ⊆ V
2		int0 4922	. . . . . . . . 9 ⊢ ∩ ∅ = V
3	1, 2	sseqtrri 3980	. . . . . . . 8 ⊢ 𝑋 ⊆ ∩ ∅
4		dfss2 3917	. . . . . . . 8 ⊢ (𝑋 ⊆ ∩ ∅ ↔ (𝑋 ∩ ∩ ∅) = 𝑋)
5	3, 4	mpbi 233	. . . . . . 7 ⊢ (𝑋 ∩ ∩ ∅) = 𝑋
6	5	eqcomi 2770	. . . . . 6 ⊢ 𝑋 = (𝑋 ∩ ∩ ∅)
7	6	eleq1i 2852	. . . . 5 ⊢ (𝑋 ∈ 𝐵 ↔ (𝑋 ∩ ∩ ∅) ∈ 𝐵)
8	7	a1i 11	. . . 4 ⊢ (𝐴 ⊆ 𝒫 𝑋 → (𝑋 ∈ 𝐵 ↔ (𝑋 ∩ ∩ ∅) ∈ 𝐵))
9		eldifsn 4748	. . . . . . . 8 ⊢ (𝑥 ∈ (𝒫 𝐴 ∖ {∅}) ↔ (𝑥 ∈ 𝒫 𝐴 ∧ 𝑥 ≠ ∅))
10		sstr2 3938	. . . . . . . . . . 11 ⊢ (𝑥 ⊆ 𝐴 → (𝐴 ⊆ 𝒫 𝑋 → 𝑥 ⊆ 𝒫 𝑋))
11		intss2 5068	. . . . . . . . . . 11 ⊢ (𝑥 ⊆ 𝒫 𝑋 → (𝑥 ≠ ∅ → ∩ 𝑥 ⊆ 𝑋))
12	10, 11	syl6 36	. . . . . . . . . 10 ⊢ (𝑥 ⊆ 𝐴 → (𝐴 ⊆ 𝒫 𝑋 → (𝑥 ≠ ∅ → ∩ 𝑥 ⊆ 𝑋)))
13		elpwi 4564	. . . . . . . . . 10 ⊢ (𝑥 ∈ 𝒫 𝐴 → 𝑥 ⊆ 𝐴)
14	12, 13	syl11 34	. . . . . . . . 9 ⊢ (𝐴 ⊆ 𝒫 𝑋 → (𝑥 ∈ 𝒫 𝐴 → (𝑥 ≠ ∅ → ∩ 𝑥 ⊆ 𝑋)))
15	14	impd 416	. . . . . . . 8 ⊢ (𝐴 ⊆ 𝒫 𝑋 → ((𝑥 ∈ 𝒫 𝐴 ∧ 𝑥 ≠ ∅) → ∩ 𝑥 ⊆ 𝑋))
16	9, 15	biimtrid 245	. . . . . . 7 ⊢ (𝐴 ⊆ 𝒫 𝑋 → (𝑥 ∈ (𝒫 𝐴 ∖ {∅}) → ∩ 𝑥 ⊆ 𝑋))
17		dfss2 3917	. . . . . . . . 9 ⊢ (∩ 𝑥 ⊆ 𝑋 ↔ (∩ 𝑥 ∩ 𝑋) = ∩ 𝑥)
18		incom 4155	. . . . . . . . . . 11 ⊢ (∩ 𝑥 ∩ 𝑋) = (𝑋 ∩ ∩ 𝑥)
19	18	eqeq1i 2766	. . . . . . . . . 10 ⊢ ((∩ 𝑥 ∩ 𝑋) = ∩ 𝑥 ↔ (𝑋 ∩ ∩ 𝑥) = ∩ 𝑥)
20		eqcom 2768	. . . . . . . . . 10 ⊢ ((𝑋 ∩ ∩ 𝑥) = ∩ 𝑥 ↔ ∩ 𝑥 = (𝑋 ∩ ∩ 𝑥))
21	19, 20	sylbb 222	. . . . . . . . 9 ⊢ ((∩ 𝑥 ∩ 𝑋) = ∩ 𝑥 → ∩ 𝑥 = (𝑋 ∩ ∩ 𝑥))
22	17, 21	sylbi 220	. . . . . . . 8 ⊢ (∩ 𝑥 ⊆ 𝑋 → ∩ 𝑥 = (𝑋 ∩ ∩ 𝑥))
23		eleq1 2849	. . . . . . . . 9 ⊢ (∩ 𝑥 = (𝑋 ∩ ∩ 𝑥) → (∩ 𝑥 ∈ 𝐵 ↔ (𝑋 ∩ ∩ 𝑥) ∈ 𝐵))
24	23	a1i 11	. . . . . . . 8 ⊢ (𝐴 ⊆ 𝒫 𝑋 → (∩ 𝑥 = (𝑋 ∩ ∩ 𝑥) → (∩ 𝑥 ∈ 𝐵 ↔ (𝑋 ∩ ∩ 𝑥) ∈ 𝐵)))
25	22, 24	syl5 35	. . . . . . 7 ⊢ (𝐴 ⊆ 𝒫 𝑋 → (∩ 𝑥 ⊆ 𝑋 → (∩ 𝑥 ∈ 𝐵 ↔ (𝑋 ∩ ∩ 𝑥) ∈ 𝐵)))
26	16, 25	syld 48	. . . . . 6 ⊢ (𝐴 ⊆ 𝒫 𝑋 → (𝑥 ∈ (𝒫 𝐴 ∖ {∅}) → (∩ 𝑥 ∈ 𝐵 ↔ (𝑋 ∩ ∩ 𝑥) ∈ 𝐵)))
27	26	ralrimiv 3154	. . . . 5 ⊢ (𝐴 ⊆ 𝒫 𝑋 → ∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})(∩ 𝑥 ∈ 𝐵 ↔ (𝑋 ∩ ∩ 𝑥) ∈ 𝐵))
28		ralbi 3118	. . . . 5 ⊢ (∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})(∩ 𝑥 ∈ 𝐵 ↔ (𝑋 ∩ ∩ 𝑥) ∈ 𝐵) → (∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})∩ 𝑥 ∈ 𝐵 ↔ ∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})(𝑋 ∩ ∩ 𝑥) ∈ 𝐵))
29	27, 28	syl 18	. . . 4 ⊢ (𝐴 ⊆ 𝒫 𝑋 → (∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})∩ 𝑥 ∈ 𝐵 ↔ ∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})(𝑋 ∩ ∩ 𝑥) ∈ 𝐵))
30	8, 29	anbi12d 644	. . 3 ⊢ (𝐴 ⊆ 𝒫 𝑋 → ((𝑋 ∈ 𝐵 ∧ ∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})∩ 𝑥 ∈ 𝐵) ↔ ((𝑋 ∩ ∩ ∅) ∈ 𝐵 ∧ ∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})(𝑋 ∩ ∩ 𝑥) ∈ 𝐵)))
31	30	biancomd 469	. 2 ⊢ (𝐴 ⊆ 𝒫 𝑋 → ((𝑋 ∈ 𝐵 ∧ ∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})∩ 𝑥 ∈ 𝐵) ↔ (∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})(𝑋 ∩ ∩ 𝑥) ∈ 𝐵 ∧ (𝑋 ∩ ∩ ∅) ∈ 𝐵)))
32		0elpw 5317	. . 3 ⊢ ∅ ∈ 𝒫 𝐴
33		inteq 4910	. . . . 5 ⊢ (𝑥 = ∅ → ∩ 𝑥 = ∩ ∅)
34		ineq2 4160	. . . . 5 ⊢ (∩ 𝑥 = ∩ ∅ → (𝑋 ∩ ∩ 𝑥) = (𝑋 ∩ ∩ ∅))
35		eleq1 2849	. . . . 5 ⊢ ((𝑋 ∩ ∩ 𝑥) = (𝑋 ∩ ∩ ∅) → ((𝑋 ∩ ∩ 𝑥) ∈ 𝐵 ↔ (𝑋 ∩ ∩ ∅) ∈ 𝐵))
36	33, 34, 35	3syl 19	. . . 4 ⊢ (𝑥 = ∅ → ((𝑋 ∩ ∩ 𝑥) ∈ 𝐵 ↔ (𝑋 ∩ ∩ ∅) ∈ 𝐵))
37	36	bj-raldifsn 38021	. . 3 ⊢ (∅ ∈ 𝒫 𝐴 → (∀𝑥 ∈ 𝒫 𝐴(𝑋 ∩ ∩ 𝑥) ∈ 𝐵 ↔ (∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})(𝑋 ∩ ∩ 𝑥) ∈ 𝐵 ∧ (𝑋 ∩ ∩ ∅) ∈ 𝐵)))
38	32, 37	ax-mp 5	. 2 ⊢ (∀𝑥 ∈ 𝒫 𝐴(𝑋 ∩ ∩ 𝑥) ∈ 𝐵 ↔ (∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})(𝑋 ∩ ∩ 𝑥) ∈ 𝐵 ∧ (𝑋 ∩ ∩ ∅) ∈ 𝐵))
39	31, 38	bitr4di 292	1 ⊢ (𝐴 ⊆ 𝒫 𝑋 → ((𝑋 ∈ 𝐵 ∧ ∀𝑥 ∈ (𝒫 𝐴 ∖ {∅})∩ 𝑥 ∈ 𝐵) ↔ ∀𝑥 ∈ 𝒫 𝐴(𝑋 ∩ ∩ 𝑥) ∈ 𝐵))

This proof depends on syntax axioms:   → wi 4   ↔ wb 209   ∧ wa 401   = wceq 1570   ∈ wcel 2145   ≠ wne 2956  ∀wral 3077  Vcvv 3451   ∖ cdif 3896   ∩ cin 3898   ⊆ wss 3899  ∅c0 4279  𝒫 cpw 4557  {csn 4584  ∩ cint 4907

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041  ax-8 2147  ax-9 2155  ax-ext 2733  ax-nul 5260

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-3an 1105  df-tru 1573  df-fal 1583  df-ex 1813  df-sb 2100  df-clab 2740  df-cleq 2753  df-clel 2836  df-ne 2957  df-ral 3078  df-rex 3088  df-rab 3414  df-v 3453  df-dif 3902  df-un 3904  df-in 3906  df-ss 3916  df-nul 4280  df-pw 4559  df-sn 4585  df-uni 4868  df-int 4908

This theorem is used by: (None)