Theorem 1st0 7999

Description: The value of the first-member function at the empty set. (Contributed by NM, 23-Apr-2007.)

Assertion

Ref	Expression
1st0	⊢ (1st ‘∅) = ∅

Proof of Theorem 1st0

Step	Hyp	Ref	Expression
1		1stval 7995	. 2 ⊢ (1st ‘∅) = ∪ dom {∅}
2		dmsn0 6203	. . 3 ⊢ dom {∅} = ∅
3	2	unieqi 4900	. 2 ⊢ ∪ dom {∅} = ∪ ∅
4		uni0 4916	. 2 ⊢ ∪ ∅ = ∅
5	1, 3, 4	3eqtri 2763	1 ⊢ (1st ‘∅) = ∅

Syntax hints:   = wceq 1540  ∅c0 4313  {csn 4606  ∪ cuni 4888  dom cdm 5659  ‘cfv 6536  1^st c1st 7991

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1795  ax-4 1809  ax-5 1910  ax-6 1967  ax-7 2008  ax-8 2111  ax-9 2119  ax-10 2142  ax-11 2158  ax-12 2178  ax-ext 2708  ax-sep 5271  ax-nul 5281  ax-pr 5407  ax-un 7734

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-3an 1088  df-tru 1543  df-fal 1553  df-ex 1780  df-nf 1784  df-sb 2066  df-mo 2540  df-eu 2569  df-clab 2715  df-cleq 2728  df-clel 2810  df-nfc 2886  df-ne 2934  df-ral 3053  df-rex 3062  df-rab 3421  df-v 3466  df-dif 3934  df-un 3936  df-in 3938  df-ss 3948  df-nul 4314  df-if 4506  df-sn 4607  df-pr 4609  df-op 4613  df-uni 4889  df-br 5125  df-opab 5187  df-mpt 5207  df-id 5553  df-xp 5665  df-rel 5666  df-cnv 5667  df-co 5668  df-dm 5669  df-rn 5670  df-iota 6489  df-fun 6538  df-fv 6544  df-1st 7993

This theorem is referenced by:  vafval  30589  fucofvalne  49216  reldmprcof1  49271  prcof1  49278