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Theorem rexxfr 4246
Description: Transfer existence from a variable 𝑥 to another variable 𝑦 contained in expression 𝐴. (Contributed by NM, 10-Jun-2005.) (Revised by Mario Carneiro, 15-Aug-2014.)
Hypotheses
Ref Expression
ralxfr.1 (𝑦𝐶𝐴𝐵)
ralxfr.2 (𝑥𝐵 → ∃𝑦𝐶 𝑥 = 𝐴)
ralxfr.3 (𝑥 = 𝐴 → (𝜑𝜓))
Assertion
Ref Expression
rexxfr (∃𝑥𝐵 𝜑 ↔ ∃𝑦𝐶 𝜓)
Distinct variable groups:   𝜓,𝑥   𝜑,𝑦   𝑥,𝐴   𝑥,𝑦,𝐵   𝑥,𝐶
Allowed substitution hints:   𝜑(𝑥)   𝜓(𝑦)   𝐴(𝑦)   𝐶(𝑦)

Proof of Theorem rexxfr
StepHypRef Expression
1 ralxfr.1 . . . 4 (𝑦𝐶𝐴𝐵)
21adantl 271 . . 3 ((⊤ ∧ 𝑦𝐶) → 𝐴𝐵)
3 ralxfr.2 . . . 4 (𝑥𝐵 → ∃𝑦𝐶 𝑥 = 𝐴)
43adantl 271 . . 3 ((⊤ ∧ 𝑥𝐵) → ∃𝑦𝐶 𝑥 = 𝐴)
5 ralxfr.3 . . . 4 (𝑥 = 𝐴 → (𝜑𝜓))
65adantl 271 . . 3 ((⊤ ∧ 𝑥 = 𝐴) → (𝜑𝜓))
72, 4, 6rexxfrd 4241 . 2 (⊤ → (∃𝑥𝐵 𝜑 ↔ ∃𝑦𝐶 𝜓))
87trud 1294 1 (∃𝑥𝐵 𝜑 ↔ ∃𝑦𝐶 𝜓)
Colors of variables: wff set class
Syntax hints:  wi 4  wb 103   = wceq 1285  wtru 1286  wcel 1434  wrex 2354
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 663  ax-5 1377  ax-7 1378  ax-gen 1379  ax-ie1 1423  ax-ie2 1424  ax-8 1436  ax-10 1437  ax-11 1438  ax-i12 1439  ax-bndl 1440  ax-4 1441  ax-17 1460  ax-i9 1464  ax-ial 1468  ax-i5r 1469  ax-ext 2065
This theorem depends on definitions:  df-bi 115  df-tru 1288  df-nf 1391  df-sb 1688  df-clab 2070  df-cleq 2076  df-clel 2079  df-nfc 2212  df-ral 2358  df-rex 2359  df-v 2612
This theorem is referenced by: (None)
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