Theorem cbvmo 2608

Description: Rule used to change bound variables, using implicit substitution. Usage of this theorem is discouraged because it depends on ax-13 2380. Use the weaker cbvmow 2607, cbvmovw 2606 when possible. (Contributed by NM, 9-Mar-1995.) (Revised by Andrew Salmon, 8-Jun-2011.) (Proof shortened by Wolf Lammen, 4-Jan-2023.) (New usage is discouraged.)

Hypotheses

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

Assertion

Ref	Expression
cbvmo	⊢ (∃*𝑥𝜑 ↔ ∃*𝑦𝜓)

Proof of Theorem cbvmo

Step	Hyp	Ref	Expression
1		cbvmo.1	. . 3 ⊢ Ⅎ𝑦𝜑
2	1	sb8mo 2605	. 2 ⊢ (∃*𝑥𝜑 ↔ ∃*𝑦[𝑦 / 𝑥]𝜑)
3		cbvmo.2	. . . 4 ⊢ Ⅎ𝑥𝜓
4		cbvmo.3	. . . 4 ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓))
5	3, 4	sbie 2510	. . 3 ⊢ ([𝑦 / 𝑥]𝜑 ↔ 𝜓)
6	5	mobii 2552	. 2 ⊢ (∃*𝑦[𝑦 / 𝑥]𝜑 ↔ ∃*𝑦𝜓)
7	2, 6	bitri 276	1 ⊢ (∃*𝑥𝜑 ↔ ∃*𝑦𝜓)

Syntax hints:   → wi 4   ↔ wb 207  Ⅎwnf 1790  [wsb 2073  ∃*wmo 2541

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1802  ax-4 1816  ax-5 1917  ax-6 1974  ax-7 2015  ax-10 2152  ax-11 2168  ax-12 2189  ax-13 2380

This theorem depends on definitions:  df-bi 208  df-an 397  df-or 854  df-tru 1550  df-ex 1787  df-nf 1791  df-sb 2074  df-mo 2543  df-eu 2573

This theorem is referenced by:  cbveuALT  2612