Theorem uniex 4359

Description: The Axiom of Union in class notation. This says that if A is a set i.e. A e. _V (see isset 2692), 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 3745	. . 3 |- ( x = A -> U. x = U. A )
3	2	eleq1d 2208	. 2 |- ( x = A -> ( U. x e. _V <-> U. A e. _V ) )
4		uniex2 4358	. . 3 |- E. y y = U. x
5	4	issetri 2695	. 2 |- U. x e. _V
6	1, 3, 5	vtocl 2740	1 |- U. A e. _V

Syntax hints:   = wceq 1331   e. wcel 1480   _Vcvv 2686   U.cuni 3736

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 698  ax-5 1423  ax-7 1424  ax-gen 1425  ax-ie1 1469  ax-ie2 1470  ax-8 1482  ax-10 1483  ax-11 1484  ax-i12 1485  ax-bndl 1486  ax-4 1487  ax-13 1491  ax-14 1492  ax-17 1506  ax-i9 1510  ax-ial 1514  ax-i5r 1515  ax-ext 2121  ax-sep 4046  ax-un 4355

This theorem depends on definitions:  df-bi 116  df-tru 1334  df-nf 1437  df-sb 1736  df-clab 2126  df-cleq 2132  df-clel 2135  df-nfc 2270  df-rex 2422  df-v 2688  df-uni 3737

This theorem is referenced by:  vuniex  4360  uniexg  4361  unex  4362  uniuni  4372  iunpw  4401  fo1st  6055  fo2nd  6056  brtpos2  6148  tfrexlem  6231  ixpsnf1o  6630  xpcomco  6720  xpassen  6724  pnfnre  7807  pnfxr  7818