Theorem bj-ceqsalt 37089

Description: Remove from ceqsalt 3475 dependency on ax-ext 2709 (and on df-cleq 2729 and df-v 3443). Note: this is not doable with ceqsralt 3476 (or ceqsralv 3482), which uses eleq1 2825, but the same dependence removal is possible for ceqsalg 3477, ceqsal 3479, ceqsalv 3481, cgsexg 3486, cgsex2g 3487, cgsex4g 3488, ceqsex 3490, ceqsexv 3491, ceqsex2 3494, ceqsex2v 3495, ceqsex3v 3496, ceqsex4v 3497, ceqsex6v 3498, ceqsex8v 3499, gencbvex 3500 (after changing 𝐴 = 𝑦 to 𝑦 = 𝐴), gencbvex2 3501, gencbval 3502, vtoclgft 3510 (it uses Ⅎ, whose justification nfcjust 2885 does not use ax-ext 2709) and several other vtocl* theorems (see for instance bj-vtoclg1f 37121). See also bj-ceqsaltv 37090. (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 37087	. 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  37093