Theorem 1stnpr 7975

Description: Value of the first-member function at non-pairs. (Contributed by Thierry Arnoux, 22-Sep-2017.)

Assertion

Ref	Expression
1stnpr	⊢ (¬ 𝐴 ∈ (V × V) → (1st ‘𝐴) = ∅)

Proof of Theorem 1stnpr

Step	Hyp	Ref	Expression
1		1stval 7973	. 2 ⊢ (1st ‘𝐴) = ∪ dom {𝐴}
2		dmsnn0 6183	. . . . . 6 ⊢ (𝐴 ∈ (V × V) ↔ dom {𝐴} ≠ ∅)
3	2	biimpri 228	. . . . 5 ⊢ (dom {𝐴} ≠ ∅ → 𝐴 ∈ (V × V))
4	3	necon1bi 2954	. . . 4 ⊢ (¬ 𝐴 ∈ (V × V) → dom {𝐴} = ∅)
5	4	unieqd 4887	. . 3 ⊢ (¬ 𝐴 ∈ (V × V) → ∪ dom {𝐴} = ∪ ∅)
6		uni0 4902	. . 3 ⊢ ∪ ∅ = ∅
7	5, 6	eqtrdi 2781	. 2 ⊢ (¬ 𝐴 ∈ (V × V) → ∪ dom {𝐴} = ∅)
8	1, 7	eqtrid 2777	1 ⊢ (¬ 𝐴 ∈ (V × V) → (1st ‘𝐴) = ∅)

Syntax hints:  ¬ wn 3   → wi 4   = wceq 1540   ∈ wcel 2109   ≠ wne 2926  Vcvv 3450  ∅c0 4299  {csn 4592  ∪ cuni 4874   × cxp 5639  dom cdm 5641  ‘cfv 6514  1^st c1st 7969

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 2702  ax-sep 5254  ax-nul 5264  ax-pr 5390  ax-un 7714

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 2534  df-eu 2563  df-clab 2709  df-cleq 2722  df-clel 2804  df-nfc 2879  df-ne 2927  df-ral 3046  df-rex 3055  df-rab 3409  df-v 3452  df-dif 3920  df-un 3922  df-in 3924  df-ss 3934  df-nul 4300  df-if 4492  df-sn 4593  df-pr 4595  df-op 4599  df-uni 4875  df-br 5111  df-opab 5173  df-mpt 5192  df-id 5536  df-xp 5647  df-rel 5648  df-cnv 5649  df-co 5650  df-dm 5651  df-rn 5652  df-iota 6467  df-fun 6516  df-fv 6522  df-1st 7971

This theorem is referenced by: (None)