Theorem iunxiun 3902

Description: Separate an indexed union in the index of an indexed union. (Contributed by Mario Carneiro, 5-Dec-2016.)

Assertion

Ref	Expression
iunxiun	⊢ ∪ 𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵𝐶 = ∪ 𝑦 ∈ 𝐴 ∪ 𝑥 ∈ 𝐵 𝐶

Distinct variable groups:   𝑥,𝑦   𝑥,𝐴   𝑦,𝐶

Allowed substitution hints:   𝐴(𝑦)   𝐵(𝑥,𝑦)   𝐶(𝑥)

Proof of Theorem iunxiun

Dummy variable 𝑧 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		eliun 3825	. . . . . . . 8 ⊢ (𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵 ↔ ∃𝑦 ∈ 𝐴 𝑥 ∈ 𝐵)
2	1	anbi1i 454	. . . . . . 7 ⊢ ((𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵 ∧ 𝑧 ∈ 𝐶) ↔ (∃𝑦 ∈ 𝐴 𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶))
3		r19.41v 2590	. . . . . . 7 ⊢ (∃𝑦 ∈ 𝐴 (𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶) ↔ (∃𝑦 ∈ 𝐴 𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶))
4	2, 3	bitr4i 186	. . . . . 6 ⊢ ((𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵 ∧ 𝑧 ∈ 𝐶) ↔ ∃𝑦 ∈ 𝐴 (𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶))
5	4	exbii 1585	. . . . 5 ⊢ (∃𝑥(𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵 ∧ 𝑧 ∈ 𝐶) ↔ ∃𝑥∃𝑦 ∈ 𝐴 (𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶))
6		rexcom4 2712	. . . . 5 ⊢ (∃𝑦 ∈ 𝐴 ∃𝑥(𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶) ↔ ∃𝑥∃𝑦 ∈ 𝐴 (𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶))
7	5, 6	bitr4i 186	. . . 4 ⊢ (∃𝑥(𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵 ∧ 𝑧 ∈ 𝐶) ↔ ∃𝑦 ∈ 𝐴 ∃𝑥(𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶))
8		df-rex 2423	. . . 4 ⊢ (∃𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵𝑧 ∈ 𝐶 ↔ ∃𝑥(𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵 ∧ 𝑧 ∈ 𝐶))
9		eliun 3825	. . . . . 6 ⊢ (𝑧 ∈ ∪ 𝑥 ∈ 𝐵 𝐶 ↔ ∃𝑥 ∈ 𝐵 𝑧 ∈ 𝐶)
10		df-rex 2423	. . . . . 6 ⊢ (∃𝑥 ∈ 𝐵 𝑧 ∈ 𝐶 ↔ ∃𝑥(𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶))
11	9, 10	bitri 183	. . . . 5 ⊢ (𝑧 ∈ ∪ 𝑥 ∈ 𝐵 𝐶 ↔ ∃𝑥(𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶))
12	11	rexbii 2445	. . . 4 ⊢ (∃𝑦 ∈ 𝐴 𝑧 ∈ ∪ 𝑥 ∈ 𝐵 𝐶 ↔ ∃𝑦 ∈ 𝐴 ∃𝑥(𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶))
13	7, 8, 12	3bitr4i 211	. . 3 ⊢ (∃𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵𝑧 ∈ 𝐶 ↔ ∃𝑦 ∈ 𝐴 𝑧 ∈ ∪ 𝑥 ∈ 𝐵 𝐶)
14		eliun 3825	. . 3 ⊢ (𝑧 ∈ ∪ 𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵𝐶 ↔ ∃𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵𝑧 ∈ 𝐶)
15		eliun 3825	. . 3 ⊢ (𝑧 ∈ ∪ 𝑦 ∈ 𝐴 ∪ 𝑥 ∈ 𝐵 𝐶 ↔ ∃𝑦 ∈ 𝐴 𝑧 ∈ ∪ 𝑥 ∈ 𝐵 𝐶)
16	13, 14, 15	3bitr4i 211	. 2 ⊢ (𝑧 ∈ ∪ 𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵𝐶 ↔ 𝑧 ∈ ∪ 𝑦 ∈ 𝐴 ∪ 𝑥 ∈ 𝐵 𝐶)
17	16	eqriv 2137	1 ⊢ ∪ 𝑥 ∈ ∪ 𝑦 ∈ 𝐴 𝐵𝐶 = ∪ 𝑦 ∈ 𝐴 ∪ 𝑥 ∈ 𝐵 𝐶

Syntax hints:   ∧ wa 103   = wceq 1332  ∃wex 1469   ∈ wcel 1481  ∃wrex 2418  ∪ ciun 3821

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 699  ax-5 1424  ax-7 1425  ax-gen 1426  ax-ie1 1470  ax-ie2 1471  ax-8 1483  ax-10 1484  ax-11 1485  ax-i12 1486  ax-bndl 1487  ax-4 1488  ax-17 1507  ax-i9 1511  ax-ial 1515  ax-i5r 1516  ax-ext 2122

This theorem depends on definitions:  df-bi 116  df-tru 1335  df-nf 1438  df-sb 1737  df-clab 2127  df-cleq 2133  df-clel 2136  df-nfc 2271  df-ral 2422  df-rex 2423  df-v 2691  df-iun 3823

This theorem is referenced by: (None)