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Theorem dmsnopg 6211
Description: The domain of a singleton of an ordered pair is the singleton of the first member. (Contributed by Mario Carneiro, 26-Apr-2015.)
Assertion
Ref Expression
dmsnopg (𝐵𝑉 → dom {⟨𝐴, 𝐵⟩} = {𝐴})

Proof of Theorem dmsnopg
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 vex 3476 . . . . . 6 𝑥 ∈ V
2 vex 3476 . . . . . 6 𝑦 ∈ V
31, 2opth1 5474 . . . . 5 (⟨𝑥, 𝑦⟩ = ⟨𝐴, 𝐵⟩ → 𝑥 = 𝐴)
43exlimiv 1931 . . . 4 (∃𝑦𝑥, 𝑦⟩ = ⟨𝐴, 𝐵⟩ → 𝑥 = 𝐴)
5 opeq1 4872 . . . . 5 (𝑥 = 𝐴 → ⟨𝑥, 𝐵⟩ = ⟨𝐴, 𝐵⟩)
6 opeq2 4873 . . . . . . 7 (𝑦 = 𝐵 → ⟨𝑥, 𝑦⟩ = ⟨𝑥, 𝐵⟩)
76eqeq1d 2732 . . . . . 6 (𝑦 = 𝐵 → (⟨𝑥, 𝑦⟩ = ⟨𝐴, 𝐵⟩ ↔ ⟨𝑥, 𝐵⟩ = ⟨𝐴, 𝐵⟩))
87spcegv 3586 . . . . 5 (𝐵𝑉 → (⟨𝑥, 𝐵⟩ = ⟨𝐴, 𝐵⟩ → ∃𝑦𝑥, 𝑦⟩ = ⟨𝐴, 𝐵⟩))
95, 8syl5 34 . . . 4 (𝐵𝑉 → (𝑥 = 𝐴 → ∃𝑦𝑥, 𝑦⟩ = ⟨𝐴, 𝐵⟩))
104, 9impbid2 225 . . 3 (𝐵𝑉 → (∃𝑦𝑥, 𝑦⟩ = ⟨𝐴, 𝐵⟩ ↔ 𝑥 = 𝐴))
111eldm2 5900 . . . 4 (𝑥 ∈ dom {⟨𝐴, 𝐵⟩} ↔ ∃𝑦𝑥, 𝑦⟩ ∈ {⟨𝐴, 𝐵⟩})
12 opex 5463 . . . . . 6 𝑥, 𝑦⟩ ∈ V
1312elsn 4642 . . . . 5 (⟨𝑥, 𝑦⟩ ∈ {⟨𝐴, 𝐵⟩} ↔ ⟨𝑥, 𝑦⟩ = ⟨𝐴, 𝐵⟩)
1413exbii 1848 . . . 4 (∃𝑦𝑥, 𝑦⟩ ∈ {⟨𝐴, 𝐵⟩} ↔ ∃𝑦𝑥, 𝑦⟩ = ⟨𝐴, 𝐵⟩)
1511, 14bitri 274 . . 3 (𝑥 ∈ dom {⟨𝐴, 𝐵⟩} ↔ ∃𝑦𝑥, 𝑦⟩ = ⟨𝐴, 𝐵⟩)
16 velsn 4643 . . 3 (𝑥 ∈ {𝐴} ↔ 𝑥 = 𝐴)
1710, 15, 163bitr4g 313 . 2 (𝐵𝑉 → (𝑥 ∈ dom {⟨𝐴, 𝐵⟩} ↔ 𝑥 ∈ {𝐴}))
1817eqrdv 2728 1 (𝐵𝑉 → dom {⟨𝐴, 𝐵⟩} = {𝐴})
Colors of variables: wff setvar class
Syntax hints:  wi 4   = wceq 1539  wex 1779  wcel 2104  {csn 4627  cop 4633  dom cdm 5675
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 1911  ax-6 1969  ax-7 2009  ax-8 2106  ax-9 2114  ax-ext 2701  ax-sep 5298  ax-nul 5305  ax-pr 5426
This theorem depends on definitions:  df-bi 206  df-an 395  df-or 844  df-3an 1087  df-tru 1542  df-fal 1552  df-ex 1780  df-sb 2066  df-clab 2708  df-cleq 2722  df-clel 2808  df-rab 3431  df-v 3474  df-dif 3950  df-un 3952  df-in 3954  df-ss 3964  df-nul 4322  df-if 4528  df-sn 4628  df-pr 4630  df-op 4634  df-br 5148  df-dm 5685
This theorem is referenced by:  dmsnopss  6212  dmpropg  6213  dmsnop  6214  rnsnopg  6219  fnsng  6599  funprg  6601  funtpg  6602  fntpg  6607  funsnfsupp  9389  s1dmALT  14563  setsval  17104  setsdm  17107  estrreslem2  18094  snstriedgval  28565  1loopgrvd0  29028  1hevtxdg0  29029  1hevtxdg1  29030  1egrvtxdg1  29033  p1evtxdeqlem  29036  wlkp1  29205  eupthp1  29736  trlsegvdeglem5  29744  cosnopne  32183  bnj96  34174  bnj535  34199  ovnovollem1  45670
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