Theorem 1stval 7170

Description: The value of the function that extracts the first member of an ordered pair. (Contributed by NM, 9-Oct-2004.) (Revised by Mario Carneiro, 8-Sep-2013.)

Assertion

Ref	Expression
1stval	|- ( 1st ` A ) = U. dom { A }

Proof of Theorem 1stval

Dummy variable x is distinct from all other variables.

Step	Hyp	Ref	Expression
1		sneq 4187	. . . . 5 |- ( x = A -> { x } = { A } )
2	1	dmeqd 5326	. . . 4 |- ( x = A -> dom { x } = dom { A } )
3	2	unieqd 4446	. . 3 |- ( x = A -> U. dom { x } = U. dom { A } )
4		df-1st 7168	. . 3 |- 1st = ( x e. _V |-> U. dom { x } )
5		snex 4908	. . . . 5 |- { A } e. _V
6	5	dmex 7099	. . . 4 |- dom { A } e. _V
7	6	uniex 6953	. . 3 |- U. dom { A } e. _V
8	3, 4, 7	fvmpt 6282	. 2 |- ( A e. _V -> ( 1st ` A ) = U. dom { A } )
9		fvprc 6185	. . 3 |- ( -. A e. _V -> ( 1st ` A ) = (/) )
10		snprc 4253	. . . . . . . 8 |- ( -. A e. _V <-> { A } = (/) )
11	10	biimpi 206	. . . . . . 7 |- ( -. A e. _V -> { A } = (/) )
12	11	dmeqd 5326	. . . . . 6 |- ( -. A e. _V -> dom { A } = dom (/) )
13		dm0 5339	. . . . . 6 |- dom (/) = (/)
14	12, 13	syl6eq 2672	. . . . 5 |- ( -. A e. _V -> dom { A } = (/) )
15	14	unieqd 4446	. . . 4 |- ( -. A e. _V -> U. dom { A } = U. (/) )
16		uni0 4465	. . . 4 |- U. (/) = (/)
17	15, 16	syl6eq 2672	. . 3 |- ( -. A e. _V -> U. dom { A } = (/) )
18	9, 17	eqtr4d 2659	. 2 |- ( -. A e. _V -> ( 1st ` A ) = U. dom { A } )
19	8, 18	pm2.61i 176	1 |- ( 1st ` A ) = U. dom { A }

Syntax hints:   -. wn 3   = wceq 1483   e. wcel 1990   _Vcvv 3200   (/)c0 3915   {csn 4177   U.cuni 4436   dom cdm 5114   ` cfv 5888   1stc1st 7166

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-8 1992  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602  ax-sep 4781  ax-nul 4789  ax-pow 4843  ax-pr 4906  ax-un 6949

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3an 1039  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881  df-eu 2474  df-mo 2475  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-ral 2917  df-rex 2918  df-rab 2921  df-v 3202  df-sbc 3436  df-dif 3577  df-un 3579  df-in 3581  df-ss 3588  df-nul 3916  df-if 4087  df-sn 4178  df-pr 4180  df-op 4184  df-uni 4437  df-br 4654  df-opab 4713  df-mpt 4730  df-id 5024  df-xp 5120  df-rel 5121  df-cnv 5122  df-co 5123  df-dm 5124  df-rn 5125  df-iota 5851  df-fun 5890  df-fv 5896  df-1st 7168

This theorem is referenced by:  1stnpr  7172  1st0  7174  op1st  7176  1st2val  7194  elxp6  7200  mpt2xopxnop0  7341