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Theorem nforOLD 2232
 Description: Obsolete proof of nfor 1822 as of 6-Oct-2021. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 11-Aug-2016.) (Proof modification is discouraged.) (New usage is discouraged.)
Hypotheses
Ref Expression
nfOLD.1 𝑥𝜑
nfOLD.2 𝑥𝜓
Assertion
Ref Expression
nforOLD 𝑥(𝜑𝜓)

Proof of Theorem nforOLD
StepHypRef Expression
1 df-or 384 . 2 ((𝜑𝜓) ↔ (¬ 𝜑𝜓))
2 nfOLD.1 . . . 4 𝑥𝜑
32nfnOLD 2198 . . 3 𝑥 ¬ 𝜑
4 nfOLD.2 . . 3 𝑥𝜓
53, 4nfimOLD 2217 . 2 𝑥𝜑𝜓)
61, 5nfxfrOLD 1825 1 𝑥(𝜑𝜓)
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   → wi 4   ∨ wo 382  ℲwnfOLD 1700 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1713  ax-4 1728  ax-5 1827  ax-6 1875  ax-7 1922  ax-10 2006  ax-12 2034 This theorem depends on definitions:  df-bi 196  df-or 384  df-ex 1696  df-nf 1701  df-nfOLD 1712 This theorem is referenced by:  nf3orOLD  2233
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