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Theorem rexxfr 4918
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 dfrex2 3025 . 2 (∃𝑥𝐵 𝜑 ↔ ¬ ∀𝑥𝐵 ¬ 𝜑)
2 dfrex2 3025 . . 3 (∃𝑦𝐶 𝜓 ↔ ¬ ∀𝑦𝐶 ¬ 𝜓)
3 ralxfr.1 . . . 4 (𝑦𝐶𝐴𝐵)
4 ralxfr.2 . . . 4 (𝑥𝐵 → ∃𝑦𝐶 𝑥 = 𝐴)
5 ralxfr.3 . . . . 5 (𝑥 = 𝐴 → (𝜑𝜓))
65notbid 307 . . . 4 (𝑥 = 𝐴 → (¬ 𝜑 ↔ ¬ 𝜓))
73, 4, 6ralxfr 4916 . . 3 (∀𝑥𝐵 ¬ 𝜑 ↔ ∀𝑦𝐶 ¬ 𝜓)
82, 7xchbinxr 324 . 2 (∃𝑦𝐶 𝜓 ↔ ¬ ∀𝑥𝐵 ¬ 𝜑)
91, 8bitr4i 267 1 (∃𝑥𝐵 𝜑 ↔ ∃𝑦𝐶 𝜓)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wb 196   = wceq 1523  wcel 2030  wral 2941  wrex 2942
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1762  ax-4 1777  ax-5 1879  ax-6 1945  ax-7 1981  ax-9 2039  ax-10 2059  ax-11 2074  ax-12 2087  ax-13 2282  ax-ext 2631
This theorem depends on definitions:  df-bi 197  df-or 384  df-an 385  df-tru 1526  df-ex 1745  df-nf 1750  df-sb 1938  df-clab 2638  df-cleq 2644  df-clel 2647  df-nfc 2782  df-ral 2946  df-rex 2947  df-v 3233
This theorem is referenced by:  infm3  11020  reeff1o  24246  moxfr  37572
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