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Theorem brdom2g 8954
Description: Dominance relation. This variation of brdomg 8955 does not require the Axiom of Union. (Contributed by NM, 15-Jun-1998.) Extract from a subproof of brdomg 8955. (Revised by BTernaryTau, 29-Nov-2024.)
Assertion
Ref Expression
brdom2g ((𝐴𝑉𝐵𝑊) → (𝐴𝐵 ↔ ∃𝑓 𝑓:𝐴1-1𝐵))
Distinct variable groups:   𝐴,𝑓   𝐵,𝑓
Allowed substitution hints:   𝑉(𝑓)   𝑊(𝑓)

Proof of Theorem brdom2g
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 f1eq2 6783 . . 3 (𝑥 = 𝐴 → (𝑓:𝑥1-1𝑦𝑓:𝐴1-1𝑦))
21exbidv 1923 . 2 (𝑥 = 𝐴 → (∃𝑓 𝑓:𝑥1-1𝑦 ↔ ∃𝑓 𝑓:𝐴1-1𝑦))
3 f1eq3 6784 . . 3 (𝑦 = 𝐵 → (𝑓:𝐴1-1𝑦𝑓:𝐴1-1𝐵))
43exbidv 1923 . 2 (𝑦 = 𝐵 → (∃𝑓 𝑓:𝐴1-1𝑦 ↔ ∃𝑓 𝑓:𝐴1-1𝐵))
5 df-dom 8944 . 2 ≼ = {⟨𝑥, 𝑦⟩ ∣ ∃𝑓 𝑓:𝑥1-1𝑦}
62, 4, 5brabg 5539 1 ((𝐴𝑉𝐵𝑊) → (𝐴𝐵 ↔ ∃𝑓 𝑓:𝐴1-1𝐵))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 205  wa 395   = wceq 1540  wex 1780  wcel 2105   class class class wbr 5148  1-1wf1 6540  cdom 8940
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1796  ax-4 1810  ax-5 1912  ax-6 1970  ax-7 2010  ax-8 2107  ax-9 2115  ax-ext 2702  ax-sep 5299  ax-nul 5306  ax-pr 5427
This theorem depends on definitions:  df-bi 206  df-an 396  df-or 845  df-3an 1088  df-tru 1543  df-fal 1553  df-ex 1781  df-sb 2067  df-clab 2709  df-cleq 2723  df-clel 2809  df-rab 3432  df-v 3475  df-dif 3951  df-un 3953  df-in 3955  df-ss 3965  df-nul 4323  df-if 4529  df-sn 4629  df-pr 4631  df-op 4635  df-br 5149  df-opab 5211  df-fn 6546  df-f 6547  df-f1 6548  df-dom 8944
This theorem is referenced by:  brdomg  8955  brdomi  8957  f1dom4g  8964  0domg  9103
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