Theorem 2alsraln0idm 17067

Description: Nested general "all some" quantifiers with class membership as their antecedents, for the same class 𝐴: 𝜑 holds for every 𝑥 and every 𝑦 in 𝐴, and 𝐴 is inhabited. (Contributed by Peter Mazsa, 28-May-2019.) (Revised by David A. Wheeler, 20-Jul-2026.)

Assertion

Ref	Expression
2alsraln0idm	⊢ (∀∃𝑥(𝑥 ∈ 𝐴 → ∀∃𝑦(𝑦 ∈ 𝐴 → 𝜑)) ↔ (∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 𝜑 ∧ ∃𝑥 𝑥 ∈ 𝐴))

Distinct variable group:   𝑥,𝑦,𝐴

Allowed substitution hints:   𝜑(𝑥,𝑦)

Proof of Theorem 2alsraln0idm

Step	Hyp	Ref	Expression
1		2alsraln0m 17066	. 2 ⊢ (∀∃𝑥(𝑥 ∈ 𝐴 → ∀∃𝑦(𝑦 ∈ 𝐴 → 𝜑)) ↔ (∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 𝜑 ∧ (∃𝑥 𝑥 ∈ 𝐴 ∧ ∃𝑦 𝑦 ∈ 𝐴)))
2		eleq1w 2299	. . . . . 6 ⊢ (𝑦 = 𝑥 → (𝑦 ∈ 𝐴 ↔ 𝑥 ∈ 𝐴))
3	2	cbvexvw 1976	. . . . 5 ⊢ (∃𝑦 𝑦 ∈ 𝐴 ↔ ∃𝑥 𝑥 ∈ 𝐴)
4	3	anbi2i 461	. . . 4 ⊢ ((∃𝑥 𝑥 ∈ 𝐴 ∧ ∃𝑦 𝑦 ∈ 𝐴) ↔ (∃𝑥 𝑥 ∈ 𝐴 ∧ ∃𝑥 𝑥 ∈ 𝐴))
5		anidm 400	. . . 4 ⊢ ((∃𝑥 𝑥 ∈ 𝐴 ∧ ∃𝑥 𝑥 ∈ 𝐴) ↔ ∃𝑥 𝑥 ∈ 𝐴)
6	4, 5	bitri 184	. . 3 ⊢ ((∃𝑥 𝑥 ∈ 𝐴 ∧ ∃𝑦 𝑦 ∈ 𝐴) ↔ ∃𝑥 𝑥 ∈ 𝐴)
7	6	anbi2i 461	. 2 ⊢ ((∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 𝜑 ∧ (∃𝑥 𝑥 ∈ 𝐴 ∧ ∃𝑦 𝑦 ∈ 𝐴)) ↔ (∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 𝜑 ∧ ∃𝑥 𝑥 ∈ 𝐴))
8	1, 7	bitri 184	1 ⊢ (∀∃𝑥(𝑥 ∈ 𝐴 → ∀∃𝑦(𝑦 ∈ 𝐴 → 𝜑)) ↔ (∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 𝜑 ∧ ∃𝑥 𝑥 ∈ 𝐴))

Syntax hints:   ∧ wa 104   ↔ wb 105  ∃wex 1545   ∈ wcel 2209  ∀wral 2528  ∀∃wals 17034

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1500  ax-7 1501  ax-gen 1502  ax-ie1 1546  ax-ie2 1547  ax-8 1557  ax-4 1563  ax-17 1579  ax-i9 1583  ax-ial 1587  ax-i5r 1588  ax-ext 2220

This theorem depends on definitions:  df-bi 117  df-tru 1405  df-nf 1514  df-cleq 2231  df-clel 2234  df-ral 2533  df-als 17036

This theorem is referenced by: (None)