Theorem cbv2 1737

Description: Rule used to change bound variables, using implicit substitution. Revised to align format of hypotheses to common style. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 3-Oct-2016.) (Revised by Wolf Lammen, 13-May-2018.)

Hypotheses

Ref	Expression
cbv2.1	⊢ Ⅎ𝑥𝜑
cbv2.2	⊢ Ⅎ𝑦𝜑
cbv2.3	⊢ (𝜑 → Ⅎ𝑦𝜓)
cbv2.4	⊢ (𝜑 → Ⅎ𝑥𝜒)
cbv2.5	⊢ (𝜑 → (𝑥 = 𝑦 → (𝜓 ↔ 𝜒)))

Assertion

Ref	Expression
cbv2	⊢ (𝜑 → (∀𝑥𝜓 ↔ ∀𝑦𝜒))

Proof of Theorem cbv2

Step	Hyp	Ref	Expression
1		cbv2.2	. . . 4 ⊢ Ⅎ𝑦𝜑
2	1	nfri 1507	. . 3 ⊢ (𝜑 → ∀𝑦𝜑)
3		cbv2.1	. . . . 5 ⊢ Ⅎ𝑥𝜑
4	3	nfal 1564	. . . 4 ⊢ Ⅎ𝑥∀𝑦𝜑
5	4	nfri 1507	. . 3 ⊢ (∀𝑦𝜑 → ∀𝑥∀𝑦𝜑)
6	2, 5	syl 14	. 2 ⊢ (𝜑 → ∀𝑥∀𝑦𝜑)
7		cbv2.3	. . . 4 ⊢ (𝜑 → Ⅎ𝑦𝜓)
8	7	nfrd 1508	. . 3 ⊢ (𝜑 → (𝜓 → ∀𝑦𝜓))
9		cbv2.4	. . . 4 ⊢ (𝜑 → Ⅎ𝑥𝜒)
10	9	nfrd 1508	. . 3 ⊢ (𝜑 → (𝜒 → ∀𝑥𝜒))
11		cbv2.5	. . 3 ⊢ (𝜑 → (𝑥 = 𝑦 → (𝜓 ↔ 𝜒)))
12	8, 10, 11	cbv2h 1736	. 2 ⊢ (∀𝑥∀𝑦𝜑 → (∀𝑥𝜓 ↔ ∀𝑦𝜒))
13	6, 12	syl 14	1 ⊢ (𝜑 → (∀𝑥𝜓 ↔ ∀𝑦𝜒))

Syntax hints:   → wi 4   ↔ wb 104  ∀wal 1341  Ⅎwnf 1448

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-5 1435  ax-7 1436  ax-gen 1437  ax-ie1 1481  ax-ie2 1482  ax-8 1492  ax-4 1498  ax-17 1514  ax-i9 1518  ax-ial 1522  ax-i5r 1523

This theorem depends on definitions:  df-bi 116  df-nf 1449

This theorem is referenced by:  cbvald  1913  cbvrald  13669