Theorem cbviotavwOLD

Description: Obsolete version of cbviotavw as of 30-Sep-2024. (Contributed by Andrew Salmon, 1-Aug-2011) (Revised by Gino Giotto, 26-Jan-2024) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypothesis	cbviotavwOLD.1	⊢ ( 𝑥 = 𝑦 → ( 𝜑 ↔ 𝜓 ) )
Assertion	cbviotavwOLD	⊢ ( ℩ 𝑥 𝜑 ) = ( ℩ 𝑦 𝜓 )

Proof

Step	Hyp	Ref	Expression
1		cbviotavwOLD.1	⊢ ( 𝑥 = 𝑦 → ( 𝜑 ↔ 𝜓 ) )
2		nfv	⊢ Ⅎ 𝑦 𝜑
3		nfv	⊢ Ⅎ 𝑥 𝜓
4	1 2 3	cbviotaw	⊢ ( ℩ 𝑥 𝜑 ) = ( ℩ 𝑦 𝜓 )