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Theorem zfregfr 9600
Description: The membership relation is well-founded on any class. (Contributed by NM, 26-Nov-1995.)
Assertion
Ref Expression
zfregfr E Fr 𝐴

Proof of Theorem zfregfr
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 dfepfr 5662 . 2 ( E Fr 𝐴 ↔ ∀𝑥((𝑥𝐴𝑥 ≠ ∅) → ∃𝑦𝑥 (𝑥𝑦) = ∅))
2 vex 3479 . . . . 5 𝑥 ∈ V
3 zfreg 9590 . . . . 5 ((𝑥 ∈ V ∧ 𝑥 ≠ ∅) → ∃𝑦𝑥 (𝑦𝑥) = ∅)
42, 3mpan 689 . . . 4 (𝑥 ≠ ∅ → ∃𝑦𝑥 (𝑦𝑥) = ∅)
5 incom 4202 . . . . . 6 (𝑦𝑥) = (𝑥𝑦)
65eqeq1i 2738 . . . . 5 ((𝑦𝑥) = ∅ ↔ (𝑥𝑦) = ∅)
76rexbii 3095 . . . 4 (∃𝑦𝑥 (𝑦𝑥) = ∅ ↔ ∃𝑦𝑥 (𝑥𝑦) = ∅)
84, 7sylib 217 . . 3 (𝑥 ≠ ∅ → ∃𝑦𝑥 (𝑥𝑦) = ∅)
98adantl 483 . 2 ((𝑥𝐴𝑥 ≠ ∅) → ∃𝑦𝑥 (𝑥𝑦) = ∅)
101, 9mpgbir 1802 1 E Fr 𝐴
Colors of variables: wff setvar class
Syntax hints:  wi 4  wa 397   = wceq 1542  wcel 2107  wne 2941  wrex 3071  Vcvv 3475  cin 3948  wss 3949  c0 4323   E cep 5580   Fr wfr 5629
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1914  ax-6 1972  ax-7 2012  ax-8 2109  ax-9 2117  ax-10 2138  ax-12 2172  ax-ext 2704  ax-sep 5300  ax-nul 5307  ax-pr 5428  ax-reg 9587
This theorem depends on definitions:  df-bi 206  df-an 398  df-or 847  df-3an 1090  df-tru 1545  df-fal 1555  df-ex 1783  df-nf 1787  df-sb 2069  df-clab 2711  df-cleq 2725  df-clel 2811  df-ne 2942  df-ral 3063  df-rex 3072  df-rab 3434  df-v 3477  df-dif 3952  df-un 3954  df-in 3956  df-ss 3966  df-nul 4324  df-if 4530  df-sn 4630  df-pr 4632  df-op 4636  df-br 5150  df-opab 5212  df-eprel 5581  df-fr 5632
This theorem is referenced by:  en2lp  9601  dford2  9615  noinfep  9655  zfregs  9727  bnj852  33932  dford5reg  34754  trelpss  43214
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