cbvrexv - Intuitionistic Logic Explorer

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Theorem cbvrexv 2578

Description: Change the bound variable of a restricted existential quantifier using implicit substitution. (Contributed by NM, 2-Jun-1998.)

**Hypothesis**
Ref	Expression
cbvralv.1	⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓))

**Assertion**
Ref	Expression
cbvrexv	⊢ (∃𝑥 ∈ 𝐴 𝜑 ↔ ∃𝑦 ∈ 𝐴 𝜓)

Distinct variable groups: 𝑥,𝐴 𝑦,𝐴 𝜑,𝑦 𝜓,𝑥 Allowed substitution hints: 𝜑(𝑥) 𝜓(𝑦)

**Proof of Theorem cbvrexv**
Step	Hyp	Ref	Expression
1		nfv 1461	. 2 ⊢ Ⅎ𝑦𝜑
2		nfv 1461	. 2 ⊢ Ⅎ𝑥𝜓
3		cbvralv.1	. 2 ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓))
4	1, 2, 3	cbvrex 2574	1 ⊢ (∃𝑥 ∈ 𝐴 𝜑 ↔ ∃𝑦 ∈ 𝐴 𝜓)

Colors of variables: wff set class

Syntax hints: → wi 4 ↔ wb 103 ∃wrex 2349

This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-io 662 ax-5 1376 ax-7 1377 ax-gen 1378 ax-ie1 1422 ax-ie2 1423 ax-8 1435 ax-10 1436 ax-11 1437 ax-i12 1438 ax-bndl 1439 ax-4 1440 ax-17 1459 ax-i9 1463 ax-ial 1467 ax-i5r 1468 ax-ext 2063

This theorem depends on definitions: df-bi 115 df-nf 1390 df-sb 1686 df-cleq 2074 df-clel 2077 df-nfc 2208 df-rex 2354