Theorem frd 5593

Description: A nonempty subset of an 𝑅-well-founded class has an 𝑅-minimal element (deduction form). (Contributed by BJ, 16-Nov-2024.)

Hypotheses

Ref	Expression
frd.fr	⊢ (𝜑 → 𝑅 Fr 𝐴)
frd.ss	⊢ (𝜑 → 𝐵 ⊆ 𝐴)
frd.ex	⊢ (𝜑 → 𝐵 ∈ 𝑉)
frd.n0	⊢ (𝜑 → 𝐵 ≠ ∅)

Assertion

Ref	Expression
frd	⊢ (𝜑 → ∃𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 ¬ 𝑦𝑅𝑥)

Distinct variable groups:   𝜑,𝑥,𝑦   𝑥,𝐴,𝑦   𝑥,𝐵,𝑦   𝑥,𝑅,𝑦

Allowed substitution hints:   𝑉(𝑥,𝑦)

Proof of Theorem frd

Dummy variable 𝑧 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		simpr 487	. . 3 ⊢ ((𝜑 ∧ 𝑧 = 𝐵) → 𝑧 = 𝐵)
2		biidd 264	. . . 4 ⊢ ((𝜑 ∧ 𝑧 = 𝐵) → (¬ 𝑦𝑅𝑥 ↔ ¬ 𝑦𝑅𝑥))
3	1, 2	raleqbidv 3326	. . 3 ⊢ ((𝜑 ∧ 𝑧 = 𝐵) → (∀𝑦 ∈ 𝑧 ¬ 𝑦𝑅𝑥 ↔ ∀𝑦 ∈ 𝐵 ¬ 𝑦𝑅𝑥))
4	1, 3	rexeqbidv 3327	. 2 ⊢ ((𝜑 ∧ 𝑧 = 𝐵) → (∃𝑥 ∈ 𝑧 ∀𝑦 ∈ 𝑧 ¬ 𝑦𝑅𝑥 ↔ ∃𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 ¬ 𝑦𝑅𝑥))
5		frd.ex	. . . 4 ⊢ (𝜑 → 𝐵 ∈ 𝑉)
6		frd.ss	. . . 4 ⊢ (𝜑 → 𝐵 ⊆ 𝐴)
7	5, 6	elpwd 4551	. . 3 ⊢ (𝜑 → 𝐵 ∈ 𝒫 𝐴)
8		frd.n0	. . . 4 ⊢ (𝜑 → 𝐵 ≠ ∅)
9		nelsn 4615	. . . 4 ⊢ (𝐵 ≠ ∅ → ¬ 𝐵 ∈ {∅})
10	8, 9	syl 17	. . 3 ⊢ (𝜑 → ¬ 𝐵 ∈ {∅})
11	7, 10	eldifd 3906	. 2 ⊢ (𝜑 → 𝐵 ∈ (𝒫 𝐴 ∖ {∅}))
12		frd.fr	. . 3 ⊢ (𝜑 → 𝑅 Fr 𝐴)
13		dffr6 5592	. . 3 ⊢ (𝑅 Fr 𝐴 ↔ ∀𝑧 ∈ (𝒫 𝐴 ∖ {∅})∃𝑥 ∈ 𝑧 ∀𝑦 ∈ 𝑧 ¬ 𝑦𝑅𝑥)
14	12, 13	sylib 220	. 2 ⊢ (𝜑 → ∀𝑧 ∈ (𝒫 𝐴 ∖ {∅})∃𝑥 ∈ 𝑧 ∀𝑦 ∈ 𝑧 ¬ 𝑦𝑅𝑥)
15	4, 11, 14	rspcdv2 3567	1 ⊢ (𝜑 → ∃𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 ¬ 𝑦𝑅𝑥)

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 398   = wceq 1550   ∈ wcel 2132   ≠ wne 2947  ∀wral 3066  ∃wrex 3076   ∖ cdif 3892   ⊆ wss 3895  ∅c0 4276  𝒫 cpw 4545  {csn 4572   class class class wbr 5090   Fr wfr 5586

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1805  ax-4 1819  ax-5 1920  ax-6 1977  ax-7 2018  ax-8 2134  ax-9 2142  ax-ext 2724

This theorem depends on definitions:  df-bi 209  df-an 399  df-tru 1553  df-ex 1790  df-sb 2081  df-clab 2731  df-cleq 2744  df-clel 2827  df-ne 2948  df-ral 3067  df-rex 3077  df-v 3446  df-dif 3898  df-ss 3912  df-pw 4547  df-sn 4573  df-fr 5589

This theorem is referenced by:  fri  5594  frxp3  8115  weiunfr  36765