Theorem dmuni 2538

Description: The domain of a union. Part of Exercise 8 of [Enderton] p. 41.

Assertion

Ref	Expression
dmuni	|- dom U.A = U.x e. A dom x

Distinct variable group(s):   x,A

Proof of Theorem dmuni

Step	Hyp	Ref	Expression
1		eluni 1922	. . . . . 6 |- (<.y, z>. e. U.A <-> E.x(<.y, z>. e. x /\ x e. A))
2	1	biex 733	. . . . 5 |- (E.z<.y, z>. e. U.A <-> E.zE.x(<.y, z>. e. x /\ x e. A))
3		excom 728	. . . . 5 |- (E.zE.x(<.y, z>. e. x /\ x e. A) <-> E.xE.z(<.y, z>. e. x /\ x e. A))
4		ancom 333	. . . . . . 7 |- ((E.z<.y, z>. e. x /\ x e. A) <-> (x e. A /\ E.z<.y, z>. e. x))
5		19.41v 963	. . . . . . 7 |- (E.z(<.y, z>. e. x /\ x e. A) <-> (E.z<.y, z>. e. x /\ x e. A))
6		visset 1350	. . . . . . . . 9 |- y e. V
7	6	eldm2 2528	. . . . . . . 8 |- (y e. dom x <-> E.z<.y, z>. e. x)
8	7	anbi2i 367	. . . . . . 7 |- ((x e. A /\ y e. dom x) <-> (x e. A /\ E.z<.y, z>. e. x))
9	4, 5, 8	3bitr4 158	. . . . . 6 |- (E.z(<.y, z>. e. x /\ x e. A) <-> (x e. A /\ y e. dom x))
10	9	biex 733	. . . . 5 |- (E.xE.z(<.y, z>. e. x /\ x e. A) <-> E.x(x e. A /\ y e. dom x))
11	2, 3, 10	3bitr 155	. . . 4 |- (E.z<.y, z>. e. U.A <-> E.x(x e. A /\ y e. dom x))
12		df-rex 1206	. . . 4 |- (E.x e. A y e. dom x <-> E.x(x e. A /\ y e. dom x))
13	11, 12	bitr4 154	. . 3 |- (E.z<.y, z>. e. U.A <-> E.x e. A y e. dom x)
14	6	eldm2 2528	. . 3 |- (y e. dom U.A <-> E.z<.y, z>. e. U.A)
15		eliun 1998	. . 3 |- (y e. U.x e. A dom x <-> E.x e. A y e. dom x)
16	13, 14, 15	3bitr4 158	. 2 |- (y e. dom U.A <-> y e. U.x e. A dom x)
17	16	cleqri 1101	1 |- dom U.A = U.x e. A dom x

Syntax hints:   /\ wa 196  E.wex 678   = wceq 1091   e. wcel 1092  E.wrex 1202  <.cop 1810  U.cuni 1919  U.ciun 1994  dom cdm 2410

This theorem is referenced by:  infxpidmlem5 4937  infxpidmlem7 4939

This theorem was proved from axioms:  ax-1 3  ax-2 4  ax-3 5  ax-mp 6  ax-4 673  ax-5 674  ax-6 675  ax-7 676  ax-gen 677  ax-8 798  ax-9 799  ax-10 800  ax-11 801  ax-12 802  ax-16 922  ax-17 925  ax-ext 1074

This theorem depends on definitions:  df-bi 128  df-or 197  df-an 198  df-ex 679  df-sb 853  df-clab 1093  df-cleq 1097  df-clel 1099  df-rex 1206  df-v 1349  df-un 1490  df-sn 1811  df-pr 1812  df-op 1815  df-uni 1920  df-iun 1996  df-br 2063  df-dm 2428

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