Theorem cbvalvw 1966

Description: Change bound variable. See cbvalv 1964 for a version with fewer disjoint variable conditions. (Contributed by NM, 9-Apr-2017.) Avoid ax-7 1494. (Revised by GG, 25-Aug-2024.)

Hypothesis

Ref	Expression
cbvalvw.1	⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓))

Assertion

Ref	Expression
cbvalvw	⊢ (∀𝑥𝜑 ↔ ∀𝑦𝜓)

Distinct variable groups:   𝑥,𝑦   𝜓,𝑥   𝜑,𝑦

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

Proof of Theorem cbvalvw

Step	Hyp	Ref	Expression
1		cbvalvw.1	. . . 4 ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓))
2	1	spv 1906	. . 3 ⊢ (∀𝑥𝜑 → 𝜓)
3	2	alrimiv 1920	. 2 ⊢ (∀𝑥𝜑 → ∀𝑦𝜓)
4	1	equcoms 1754	. . . . 5 ⊢ (𝑦 = 𝑥 → (𝜑 ↔ 𝜓))
5	4	biimprd 158	. . . 4 ⊢ (𝑦 = 𝑥 → (𝜓 → 𝜑))
6	5	spimv 1857	. . 3 ⊢ (∀𝑦𝜓 → 𝜑)
7	6	alrimiv 1920	. 2 ⊢ (∀𝑦𝜓 → ∀𝑥𝜑)
8	3, 7	impbii 126	1 ⊢ (∀𝑥𝜑 ↔ ∀𝑦𝜓)

Syntax hints:   → wi 4   ↔ wb 105  ∀wal 1393

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 1493  ax-gen 1495  ax-ie1 1539  ax-ie2 1540  ax-8 1550  ax-4 1556  ax-17 1572  ax-i9 1576  ax-ial 1580

This theorem depends on definitions:  df-bi 117  df-nf 1507

This theorem is referenced by:  cbvaldvaw  1977  cbval2vw  1979  cbvralvw  2769  cbvreuvw  2771