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Theorem cbval2v 2355
Description: Version of cbval2 2426 with a disjoint variable condition, which does not require ax-13 2383. (Contributed by BJ, 16-Jun-2019.) (Proof shortened by Gino Giotto, 10-Jan-2024.)
Hypotheses
Ref Expression
cbval2v.1 𝑧𝜑
cbval2v.2 𝑤𝜑
cbval2v.3 𝑥𝜓
cbval2v.4 𝑦𝜓
cbval2v.5 ((𝑥 = 𝑧𝑦 = 𝑤) → (𝜑𝜓))
Assertion
Ref Expression
cbval2v (∀𝑥𝑦𝜑 ↔ ∀𝑧𝑤𝜓)
Distinct variable group:   𝑥,𝑦,𝑧,𝑤
Allowed substitution hints:   𝜑(𝑥,𝑦,𝑧,𝑤)   𝜓(𝑥,𝑦,𝑧,𝑤)

Proof of Theorem cbval2v
StepHypRef Expression
1 cbval2v.1 . . 3 𝑧𝜑
21nfal 2334 . 2 𝑧𝑦𝜑
3 cbval2v.3 . . 3 𝑥𝜓
43nfal 2334 . 2 𝑥𝑤𝜓
5 nfv 1906 . . 3 𝑦 𝑥 = 𝑧
6 nfv 1906 . . 3 𝑤 𝑥 = 𝑧
7 cbval2v.2 . . . 4 𝑤𝜑
87a1i 11 . . 3 (𝑥 = 𝑧 → Ⅎ𝑤𝜑)
9 cbval2v.4 . . . 4 𝑦𝜓
109a1i 11 . . 3 (𝑥 = 𝑧 → Ⅎ𝑦𝜓)
11 cbval2v.5 . . . 4 ((𝑥 = 𝑧𝑦 = 𝑤) → (𝜑𝜓))
1211ex 413 . . 3 (𝑥 = 𝑧 → (𝑦 = 𝑤 → (𝜑𝜓)))
135, 6, 8, 10, 12cbv2w 2349 . 2 (𝑥 = 𝑧 → (∀𝑦𝜑 ↔ ∀𝑤𝜓))
142, 4, 13cbvalv1 2353 1 (∀𝑥𝑦𝜑 ↔ ∀𝑧𝑤𝜓)
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 207  wa 396  wal 1526  wnf 1775
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-10 2136  ax-11 2151  ax-12 2167
This theorem depends on definitions:  df-bi 208  df-an 397  df-or 842  df-ex 1772  df-nf 1776
This theorem is referenced by:  cbvex2v  2357  bj-cbval2vv  34021  eqrelf  35400
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