Theorem uniex 4502

Description: The Axiom of Union in class notation. This says that if A is a set i.e. A e. _V (see isset 2783), then the union of A is also a set. Same as Axiom 3 of [TakeutiZaring] p. 16. (Contributed by NM, 11-Aug-1993.)

Hypothesis

Ref	Expression
uniex.1	|- A e. _V

Assertion

Ref	Expression
uniex	|- U. A e. _V

Proof of Theorem uniex

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

Step	Hyp	Ref	Expression
1		uniex.1	. 2 |- A e. _V
2		unieq 3873	. . 3 |- ( x = A -> U. x = U. A )
3	2	eleq1d 2276	. 2 |- ( x = A -> ( U. x e. _V <-> U. A e. _V ) )
4		uniex2 4501	. . 3 |- E. y y = U. x
5	4	issetri 2786	. 2 |- U. x e. _V
6	1, 3, 5	vtocl 2832	1 |- U. A e. _V

Syntax hints:   = wceq 1373   e. wcel 2178   _Vcvv 2776   U.cuni 3864

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 711  ax-5 1471  ax-7 1472  ax-gen 1473  ax-ie1 1517  ax-ie2 1518  ax-8 1528  ax-10 1529  ax-11 1530  ax-i12 1531  ax-bndl 1533  ax-4 1534  ax-17 1550  ax-i9 1554  ax-ial 1558  ax-i5r 1559  ax-13 2180  ax-14 2181  ax-ext 2189  ax-sep 4178  ax-un 4498

This theorem depends on definitions:  df-bi 117  df-tru 1376  df-nf 1485  df-sb 1787  df-clab 2194  df-cleq 2200  df-clel 2203  df-nfc 2339  df-rex 2492  df-v 2778  df-uni 3865

This theorem is referenced by:  vuniex  4503  uniexg  4504  unex  4506  uniuni  4516  iunpw  4545  fo1st  6266  fo2nd  6267  brtpos2  6360  tfrexlem  6443  ixpsnf1o  6846  xpcomco  6946  xpassen  6950  pnfnre  8149  pnfxr  8160  prdsvallem  13219  prdsval  13220