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Theorem exanOLDOLD 2205
 Description: Obsolete proof of exan 1828 as of 7-Jul-2021. (Contributed by NM, 18-Aug-1993.) (Proof shortened by Andrew Salmon, 25-May-2011.) (Proof shortened by Wolf Lammen, 13-Jan-2018.) (Proof modification is discouraged.) (New usage is discouraged.)
Hypothesis
Ref Expression
exanOLDOLD.1 (∃𝑥𝜑𝜓)
Assertion
Ref Expression
exanOLDOLD 𝑥(𝜑𝜓)

Proof of Theorem exanOLDOLD
StepHypRef Expression
1 exanOLDOLD.1 . 2 (∃𝑥𝜑𝜓)
21simpri 477 . . . 4 𝜓
32nfth 1767 . . 3 𝑥𝜓
4319.41 2141 . 2 (∃𝑥(𝜑𝜓) ↔ (∃𝑥𝜑𝜓))
51, 4mpbir 221 1 𝑥(𝜑𝜓)
 Colors of variables: wff setvar class Syntax hints:   ∧ wa 383  ∃wex 1744 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-12 2087 This theorem depends on definitions:  df-bi 197  df-an 385  df-ex 1745  df-nf 1750 This theorem is referenced by: (None)
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