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Theorem frminex 5528
Description: If an element of a well-founded set satisfies a property 𝜑, then there is a minimal element that satisfies 𝜑. (Contributed by Jeff Madsen, 18-Jun-2010.) (Proof shortened by Mario Carneiro, 18-Nov-2016.)
Hypotheses
Ref Expression
frminex.1 𝐴 ∈ V
frminex.2 (𝑥 = 𝑦 → (𝜑𝜓))
Assertion
Ref Expression
frminex (𝑅 Fr 𝐴 → (∃𝑥𝐴 𝜑 → ∃𝑥𝐴 (𝜑 ∧ ∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑥))))
Distinct variable groups:   𝑥,𝐴,𝑦   𝑥,𝑅,𝑦   𝜑,𝑦   𝜓,𝑥
Allowed substitution hints:   𝜑(𝑥)   𝜓(𝑦)

Proof of Theorem frminex
Dummy variable 𝑧 is distinct from all other variables.
StepHypRef Expression
1 rabn0 4336 . 2 ({𝑥𝐴𝜑} ≠ ∅ ↔ ∃𝑥𝐴 𝜑)
2 frminex.1 . . . . 5 𝐴 ∈ V
32rabex 5226 . . . 4 {𝑥𝐴𝜑} ∈ V
4 ssrab2 4053 . . . 4 {𝑥𝐴𝜑} ⊆ 𝐴
5 fri 5510 . . . . . 6 ((({𝑥𝐴𝜑} ∈ V ∧ 𝑅 Fr 𝐴) ∧ ({𝑥𝐴𝜑} ⊆ 𝐴 ∧ {𝑥𝐴𝜑} ≠ ∅)) → ∃𝑧 ∈ {𝑥𝐴𝜑}∀𝑦 ∈ {𝑥𝐴𝜑} ¬ 𝑦𝑅𝑧)
6 frminex.2 . . . . . . . . 9 (𝑥 = 𝑦 → (𝜑𝜓))
76ralrab 3682 . . . . . . . 8 (∀𝑦 ∈ {𝑥𝐴𝜑} ¬ 𝑦𝑅𝑧 ↔ ∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑧))
87rexbii 3244 . . . . . . 7 (∃𝑧 ∈ {𝑥𝐴𝜑}∀𝑦 ∈ {𝑥𝐴𝜑} ¬ 𝑦𝑅𝑧 ↔ ∃𝑧 ∈ {𝑥𝐴𝜑}∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑧))
9 breq2 5061 . . . . . . . . . . 11 (𝑧 = 𝑥 → (𝑦𝑅𝑧𝑦𝑅𝑥))
109notbid 319 . . . . . . . . . 10 (𝑧 = 𝑥 → (¬ 𝑦𝑅𝑧 ↔ ¬ 𝑦𝑅𝑥))
1110imbi2d 342 . . . . . . . . 9 (𝑧 = 𝑥 → ((𝜓 → ¬ 𝑦𝑅𝑧) ↔ (𝜓 → ¬ 𝑦𝑅𝑥)))
1211ralbidv 3194 . . . . . . . 8 (𝑧 = 𝑥 → (∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑧) ↔ ∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑥)))
1312rexrab2 3690 . . . . . . 7 (∃𝑧 ∈ {𝑥𝐴𝜑}∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑧) ↔ ∃𝑥𝐴 (𝜑 ∧ ∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑥)))
148, 13bitri 276 . . . . . 6 (∃𝑧 ∈ {𝑥𝐴𝜑}∀𝑦 ∈ {𝑥𝐴𝜑} ¬ 𝑦𝑅𝑧 ↔ ∃𝑥𝐴 (𝜑 ∧ ∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑥)))
155, 14sylib 219 . . . . 5 ((({𝑥𝐴𝜑} ∈ V ∧ 𝑅 Fr 𝐴) ∧ ({𝑥𝐴𝜑} ⊆ 𝐴 ∧ {𝑥𝐴𝜑} ≠ ∅)) → ∃𝑥𝐴 (𝜑 ∧ ∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑥)))
1615an4s 656 . . . 4 ((({𝑥𝐴𝜑} ∈ V ∧ {𝑥𝐴𝜑} ⊆ 𝐴) ∧ (𝑅 Fr 𝐴 ∧ {𝑥𝐴𝜑} ≠ ∅)) → ∃𝑥𝐴 (𝜑 ∧ ∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑥)))
173, 4, 16mpanl12 698 . . 3 ((𝑅 Fr 𝐴 ∧ {𝑥𝐴𝜑} ≠ ∅) → ∃𝑥𝐴 (𝜑 ∧ ∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑥)))
1817ex 413 . 2 (𝑅 Fr 𝐴 → ({𝑥𝐴𝜑} ≠ ∅ → ∃𝑥𝐴 (𝜑 ∧ ∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑥))))
191, 18syl5bir 244 1 (𝑅 Fr 𝐴 → (∃𝑥𝐴 𝜑 → ∃𝑥𝐴 (𝜑 ∧ ∀𝑦𝐴 (𝜓 → ¬ 𝑦𝑅𝑥))))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wb 207  wa 396  wcel 2105  wne 3013  wral 3135  wrex 3136  {crab 3139  Vcvv 3492  wss 3933  c0 4288   class class class wbr 5057   Fr wfr 5504
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1787  ax-4 1801  ax-5 1902  ax-6 1961  ax-7 2006  ax-8 2107  ax-9 2115  ax-10 2136  ax-11 2151  ax-12 2167  ax-ext 2790  ax-sep 5194
This theorem depends on definitions:  df-bi 208  df-an 397  df-or 842  df-3an 1081  df-tru 1531  df-ex 1772  df-nf 1776  df-sb 2061  df-clab 2797  df-cleq 2811  df-clel 2890  df-nfc 2960  df-ne 3014  df-ral 3140  df-rex 3141  df-rab 3144  df-v 3494  df-dif 3936  df-un 3938  df-in 3940  df-ss 3949  df-nul 4289  df-if 4464  df-sn 4558  df-pr 4560  df-op 4564  df-br 5058  df-fr 5507
This theorem is referenced by: (None)
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