Theorem cbvmow 2629

Description: Rule used to change bound variables, using implicit substitution. Version of cbvmo 2630 with a disjoint variable condition, which does not require ax-10 2178, ax-13 2402. (Contributed by NM, 9-Mar-1995.) (Revised by GG, 23-May-2024.)

Hypotheses

Ref	Expression
cbvmow.1	⊢ Ⅎ𝑦𝜑
cbvmow.2	⊢ Ⅎ𝑥𝜓
cbvmow.3	⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓))

Assertion

Ref	Expression
cbvmow	⊢ (∃*𝑥𝜑 ↔ ∃*𝑦𝜓)

Distinct variable group:   𝑥,𝑦

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

Proof of Theorem cbvmow

Dummy variable 𝑧 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		cbvmow.1	. . . . 5 ⊢ Ⅎ𝑦𝜑
2		nfv 1947	. . . . 5 ⊢ Ⅎ𝑦 𝑥 = 𝑧
3	1, 2	nfim 1929	. . . 4 ⊢ Ⅎ𝑦(𝜑 → 𝑥 = 𝑧)
4		cbvmow.2	. . . . 5 ⊢ Ⅎ𝑥𝜓
5		nfv 1947	. . . . 5 ⊢ Ⅎ𝑥 𝑦 = 𝑧
6	4, 5	nfim 1929	. . . 4 ⊢ Ⅎ𝑥(𝜓 → 𝑦 = 𝑧)
7		cbvmow.3	. . . . 5 ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓))
8		equequ1 2058	. . . . 5 ⊢ (𝑥 = 𝑦 → (𝑥 = 𝑧 ↔ 𝑦 = 𝑧))
9	7, 8	imbi12d 347	. . . 4 ⊢ (𝑥 = 𝑦 → ((𝜑 → 𝑥 = 𝑧) ↔ (𝜓 → 𝑦 = 𝑧)))
10	3, 6, 9	cbvalv1 2371	. . 3 ⊢ (∀𝑥(𝜑 → 𝑥 = 𝑧) ↔ ∀𝑦(𝜓 → 𝑦 = 𝑧))
11	10	exbii 1881	. 2 ⊢ (∃𝑧∀𝑥(𝜑 → 𝑥 = 𝑧) ↔ ∃𝑧∀𝑦(𝜓 → 𝑦 = 𝑧))
12		dfmo 2566	. 2 ⊢ (∃*𝑥𝜑 ↔ ∃𝑧∀𝑥(𝜑 → 𝑥 = 𝑧))
13		dfmo 2566	. 2 ⊢ (∃*𝑦𝜓 ↔ ∃𝑧∀𝑦(𝜓 → 𝑦 = 𝑧))
14	11, 12, 13	3bitr4i 306	1 ⊢ (∃*𝑥𝜑 ↔ ∃*𝑦𝜓)

This proof depends on syntax axioms:   → wi 4   ↔ wb 209  ∀wal 1568  ∃wex 1812  Ⅎwnf 1816  ∃*wmo 2563

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041  ax-11 2194  ax-12 2213

This proof depends on definitions:  df-bi 210  df-an 402  df-ex 1813  df-nf 1817  df-mo 2565

This theorem is used by:  cbveuw  2632  cbvrmow  3391  dffun6f  6546  opabiotafun  6957  2ndcdisj  23755  cbvdisjf  33147  phpreu  38495  mo0sn  49870  isthincd2lem1  50477