Theorem cbviotav 4346

Description: Change bound variables in a description binder. (Contributed by Andrew Salmon, 1-Aug-2011.)

Hypothesis

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

Assertion

Ref	Expression
cbviotav	⊢ (℩xφ) = (℩yψ)

Distinct variable groups:   φ,y   ψ,x

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

Proof of Theorem cbviotav

Step	Hyp	Ref	Expression
1		cbviotav.1	. 2 ⊢ (x = y → (φ ↔ ψ))
2		nfv 1619	. 2 ⊢ Ⅎyφ
3		nfv 1619	. 2 ⊢ Ⅎxψ
4	1, 2, 3	cbviota 4345	1 ⊢ (℩xφ) = (℩yψ)

Syntax hints:   → wi 4   ↔ wb 176   = wceq 1642  ℩cio 4338

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2479  df-rex 2621  df-sn 3742  df-uni 3893  df-iota 4340

This theorem is referenced by: (None)