Theorem bj-ceqsalt 37161

Description: Remove from ceqsalt 3476 dependency on ax-ext 2709 (and on df-cleq 2729 and df-v 3444). Note: this is not doable with ceqsralt 3477 (or ceqsralv 3483), which uses eleq1 2825, but the same dependence removal is possible for ceqsalg 3478, ceqsal 3480, ceqsalv 3482, cgsexg 3487, cgsex2g 3488, cgsex4g 3489, ceqsex 3491, ceqsexv 3492, ceqsex2 3495, ceqsex2v 3496, ceqsex3v 3497, ceqsex4v 3498, ceqsex6v 3499, ceqsex8v 3500, gencbvex 3501 (after changing 𝐴 = 𝑦 to 𝑦 = 𝐴), gencbvex2 3502, gencbval 3503, vtoclgft 3511 (it uses Ⅎ, whose justification nfcjust 2885 does not use ax-ext 2709) and several other vtocl* theorems (see for instance bj-vtoclg1f 37193). See also bj-ceqsaltv 37162. (Contributed by BJ, 16-Jun-2019.) (Proof modification is discouraged.)

Assertion

Ref	Expression
bj-ceqsalt	⊢ ((Ⅎ𝑥𝜓 ∧ ∀𝑥(𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) ∧ 𝐴 ∈ 𝑉) → (∀𝑥(𝑥 = 𝐴 → 𝜑) ↔ 𝜓))

Distinct variable group:   𝑥,𝐴

Allowed substitution hints:   𝜑(𝑥)   𝜓(𝑥)   𝑉(𝑥)

Proof of Theorem bj-ceqsalt

Step	Hyp	Ref	Expression
1		elisset 2819	. . 3 ⊢ (𝐴 ∈ 𝑉 → ∃𝑥 𝑥 = 𝐴)
2	1	3anim3i 1155	. 2 ⊢ ((Ⅎ𝑥𝜓 ∧ ∀𝑥(𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) ∧ 𝐴 ∈ 𝑉) → (Ⅎ𝑥𝜓 ∧ ∀𝑥(𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) ∧ ∃𝑥 𝑥 = 𝐴))
3		bj-ceqsalt0 37159	. 2 ⊢ ((Ⅎ𝑥𝜓 ∧ ∀𝑥(𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) ∧ ∃𝑥 𝑥 = 𝐴) → (∀𝑥(𝑥 = 𝐴 → 𝜑) ↔ 𝜓))
4	2, 3	syl 17	1 ⊢ ((Ⅎ𝑥𝜓 ∧ ∀𝑥(𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) ∧ 𝐴 ∈ 𝑉) → (∀𝑥(𝑥 = 𝐴 → 𝜑) ↔ 𝜓))

Syntax hints:   → wi 4   ↔ wb 206   ∧ w3a 1087  ∀wal 1540   = wceq 1542  ∃wex 1781  Ⅎwnf 1785   ∈ wcel 2114

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1912  ax-6 1969  ax-7 2010  ax-8 2116  ax-12 2185

This theorem depends on definitions:  df-bi 207  df-an 396  df-3an 1089  df-tru 1545  df-ex 1782  df-nf 1786  df-sb 2069  df-clab 2716  df-clel 2812

This theorem is referenced by:  bj-ceqsalgALT  37165