Theorem brdom2g 6997

Description: Dominance relation. This variation of brdomg 6998 does not require the Axiom of Union. (Contributed by NM, 15-Jun-1998.) Extract from a subproof of brdomg 6998. (Revised by BTernaryTau, 29-Nov-2024.)

Assertion

Ref	Expression
brdom2g	|- ( ( A e. V /\ B e. W ) -> ( A ~<_ B <-> E. f f : A -1-1-> B ) )

Distinct variable groups:   A, f   B, f

Allowed substitution hints:   V( f)   W( f)

Proof of Theorem brdom2g

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

Step	Hyp	Ref	Expression
1		f1eq2 5574	. . 3 |- ( x = A -> ( f : x -1-1-> y <-> f : A -1-1-> y ) )
2	1	exbidv 1874	. 2 |- ( x = A -> ( E. f f : x -1-1-> y <-> E. f f : A -1-1-> y ) )
3		f1eq3 5575	. . 3 |- ( y = B -> ( f : A -1-1-> y <-> f : A -1-1-> B ) )
4	3	exbidv 1874	. 2 |- ( y = B -> ( E. f f : A -1-1-> y <-> E. f f : A -1-1-> B ) )
5		df-dom 6990	. 2 |- ~<_ = { <. x , y >. | E. f f : x -1-1-> y }
6	2, 4, 5	brabg 4392	1 |- ( ( A e. V /\ B e. W ) -> ( A ~<_ B <-> E. f f : A -1-1-> B ) )

Syntax hints:   -> wi 4   /\ wa 104   <-> wb 105   = wceq 1398   E.wex 1541   e. wcel 2205   class class class wbr 4114   -1-1->wf1 5354   ~<_ cdom 6987

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 717  ax-5 1496  ax-7 1497  ax-gen 1498  ax-ie1 1542  ax-ie2 1543  ax-8 1553  ax-10 1554  ax-11 1555  ax-i12 1556  ax-bndl 1558  ax-4 1559  ax-17 1575  ax-i9 1579  ax-ial 1583  ax-i5r 1584  ax-14 2208  ax-ext 2216  ax-sep 4233  ax-pow 4292  ax-pr 4327

This theorem depends on definitions:  df-bi 117  df-3an 1007  df-tru 1401  df-nf 1510  df-sb 1812  df-eu 2085  df-mo 2086  df-clab 2221  df-cleq 2227  df-clel 2230  df-nfc 2375  df-v 2817  df-un 3218  df-in 3220  df-ss 3227  df-pw 3676  df-sn 3700  df-pr 3701  df-op 3703  df-br 4115  df-opab 4177  df-fn 5360  df-f 5361  df-f1 5362  df-dom 6990

This theorem is referenced by:  f1dom4g  7005