Theorem cbvex-P7.VR2of2 1068

Description: cbvex-P7 1066 with one variable restriction. †

'𝑦' cannot occur in '𝜑'.

Hypotheses

Ref	Expression
cbvex-P7.VR2of2.1	⊢ Ⅎ𝑥𝜓
cbvex-P7.VR2of2.2	⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓))

Assertion

Ref	Expression
cbvex-P7.VR2of2	⊢ (∃𝑥𝜑 ↔ ∃𝑦𝜓)

Distinct variable groups:   𝜑,𝑦   𝑥,𝑦

Proof of Theorem cbvex-P7.VR2of2

Step	Hyp	Ref	Expression
1		cbvex-P7.VR2of2.1	. 2 ⊢ Ⅎ𝑥𝜓
2		ndnfrv-P7.1 826	. 2 ⊢ Ⅎ𝑦𝜑
3		cbvex-P7.VR2of2.2	. 2 ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓))
4	1, 2, 3	cbvex-P7 1066	1 ⊢ (∃𝑥𝜑 ↔ ∃𝑦𝜓)

Syntax hints:  term-obj 1   = wff-equals 6   → wff-imp 10   ↔ wff-bi 104  ∃wff-exists 595  Ⅎwff-nfree 681

This theorem was proved from axioms:  ax-L1 11  ax-L2 12  ax-L3 13  ax-MP 14  ax-GEN 15  ax-L4 16  ax-L5 17  ax-L6 18  ax-L7 19  ax-L10 27  ax-L11 28  ax-L12 29

This theorem depends on definitions:  df-bi-D2.1 107  df-and-D2.2 133  df-or-D2.3 145  df-true-D2.4 155  df-rcp-AND3 161  df-exists-D5.1 596  df-nfree-D6.1 682  df-psub-D6.2 716

This theorem is referenced by: (None)