Theorem uniprg 3804

Description: The union of a pair is the union of its members. Proposition 5.7 of [TakeutiZaring] p. 16. (Contributed by NM, 25-Aug-2006.)

Assertion

Ref	Expression
uniprg	|- ( ( A e. V /\ B e. W ) -> U. { A , B } = ( A u. B ) )

Proof of Theorem uniprg

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

Step	Hyp	Ref	Expression
1		preq1 3653	. . . 4 |- ( x = A -> { x , y } = { A , y } )
2	1	unieqd 3800	. . 3 |- ( x = A -> U. { x , y } = U. { A , y } )
3		uneq1 3269	. . 3 |- ( x = A -> ( x u. y ) = ( A u. y ) )
4	2, 3	eqeq12d 2180	. 2 |- ( x = A -> ( U. { x , y } = ( x u. y ) <-> U. { A , y } = ( A u. y ) ) )
5		preq2 3654	. . . 4 |- ( y = B -> { A , y } = { A , B } )
6	5	unieqd 3800	. . 3 |- ( y = B -> U. { A , y } = U. { A , B } )
7		uneq2 3270	. . 3 |- ( y = B -> ( A u. y ) = ( A u. B ) )
8	6, 7	eqeq12d 2180	. 2 |- ( y = B -> ( U. { A , y } = ( A u. y ) <-> U. { A , B } = ( A u. B ) ) )
9		vex 2729	. . 3 |- x e. _V
10		vex 2729	. . 3 |- y e. _V
11	9, 10	unipr 3803	. 2 |- U. { x , y } = ( x u. y )
12	4, 8, 11	vtocl2g 2790	1 |- ( ( A e. V /\ B e. W ) -> U. { A , B } = ( A u. B ) )

Syntax hints:   -> wi 4   /\ wa 103   = wceq 1343   e. wcel 2136   u. cun 3114   {cpr 3577   U.cuni 3789

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 1435  ax-7 1436  ax-gen 1437  ax-ie1 1481  ax-ie2 1482  ax-8 1492  ax-10 1493  ax-11 1494  ax-i12 1495  ax-bndl 1497  ax-4 1498  ax-17 1514  ax-i9 1518  ax-ial 1522  ax-i5r 1523  ax-ext 2147

This theorem depends on definitions:  df-bi 116  df-tru 1346  df-nf 1449  df-sb 1751  df-clab 2152  df-cleq 2158  df-clel 2161  df-nfc 2297  df-rex 2450  df-v 2728  df-un 3120  df-sn 3582  df-pr 3583  df-uni 3790

This theorem is referenced by:  onun2  4467  unopn  12643