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Theorem cbvrexv 3355
Description: Change the bound variable of a restricted existential quantifier using implicit substitution. See cbvrexvw 3229 based on fewer axioms , but extra disjoint variables. Usage of this theorem is discouraged because it depends on ax-13 2365. Use the weaker cbvrexvw 3229 when possible. (Contributed by NM, 2-Jun-1998.) (New usage is discouraged.)
Hypothesis
Ref Expression
cbvralv.1 (𝑥 = 𝑦 → (𝜑𝜓))
Assertion
Ref Expression
cbvrexv (∃𝑥𝐴 𝜑 ↔ ∃𝑦𝐴 𝜓)
Distinct variable groups:   𝑥,𝐴   𝑦,𝐴   𝜑,𝑦   𝜓,𝑥
Allowed substitution hints:   𝜑(𝑥)   𝜓(𝑦)

Proof of Theorem cbvrexv
StepHypRef Expression
1 nfv 1909 . 2 𝑦𝜑
2 nfv 1909 . 2 𝑥𝜓
3 cbvralv.1 . 2 (𝑥 = 𝑦 → (𝜑𝜓))
41, 2, 3cbvrex 3353 1 (∃𝑥𝐴 𝜑 ↔ ∃𝑦𝐴 𝜓)
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 205  wrex 3064
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1789  ax-4 1803  ax-5 1905  ax-6 1963  ax-7 2003  ax-8 2100  ax-10 2129  ax-11 2146  ax-12 2163  ax-13 2365
This theorem depends on definitions:  df-bi 206  df-an 396  df-or 845  df-tru 1536  df-ex 1774  df-nf 1778  df-sb 2060  df-clel 2804  df-nfc 2879  df-ral 3056  df-rex 3065
This theorem is referenced by:  cbvrex2v  3359  rexlimdvaacbv  43514
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