Theorem 0xp 4798

Description: The cross product with the empty set is empty. Part of Theorem 3.13(ii) of [Monk1] p. 37. (Contributed by NM, 4-Jul-1994.)

Assertion

Ref	Expression
0xp	|- ( (/) X. A ) = (/)

Proof of Theorem 0xp

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

Step	Hyp	Ref	Expression
1		elxp 4735	. . 3 |- ( z e. ( (/) X. A ) <-> E. x E. y ( z = <. x , y >. /\ ( x e. (/) /\ y e. A ) ) )
2		noel 3495	. . . . . . 7 |- -. x e. (/)
3		simprl 529	. . . . . . 7 |- ( ( z = <. x , y >. /\ ( x e. (/) /\ y e. A ) ) -> x e. (/) )
4	2, 3	mto 666	. . . . . 6 |- -. ( z = <. x , y >. /\ ( x e. (/) /\ y e. A ) )
5	4	nex 1546	. . . . 5 |- -. E. y ( z = <. x , y >. /\ ( x e. (/) /\ y e. A ) )
6	5	nex 1546	. . . 4 |- -. E. x E. y ( z = <. x , y >. /\ ( x e. (/) /\ y e. A ) )
7		noel 3495	. . . 4 |- -. z e. (/)
8	6, 7	2false 706	. . 3 |- ( E. x E. y ( z = <. x , y >. /\ ( x e. (/) /\ y e. A ) ) <-> z e. (/) )
9	1, 8	bitri 184	. 2 |- ( z e. ( (/) X. A ) <-> z e. (/) )
10	9	eqriv 2226	1 |- ( (/) X. A ) = (/)

Syntax hints:   /\ wa 104   = wceq 1395   E.wex 1538   e. wcel 2200   (/)c0 3491   <.cop 3669   X. cxp 4716

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-in1 617  ax-in2 618  ax-io 714  ax-5 1493  ax-7 1494  ax-gen 1495  ax-ie1 1539  ax-ie2 1540  ax-8 1550  ax-10 1551  ax-11 1552  ax-i12 1553  ax-bndl 1555  ax-4 1556  ax-17 1572  ax-i9 1576  ax-ial 1580  ax-i5r 1581  ax-14 2203  ax-ext 2211  ax-sep 4201  ax-pow 4257  ax-pr 4292

This theorem depends on definitions:  df-bi 117  df-3an 1004  df-tru 1398  df-fal 1401  df-nf 1507  df-sb 1809  df-clab 2216  df-cleq 2222  df-clel 2225  df-nfc 2361  df-v 2801  df-dif 3199  df-un 3201  df-in 3203  df-ss 3210  df-nul 3492  df-pw 3651  df-sn 3672  df-pr 3673  df-op 3675  df-opab 4145  df-xp 4724

This theorem is referenced by:  res0  5008  xp0  5147  xpeq0r  5150  xpdisj1  5152  xpima1  5174  xpfi  7090  exmidfodomrlemim  7375  hashxp  11043