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Theorem pm2.54 387
Description: Theorem *2.54 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm2.54 ((¬ 𝜑𝜓) → (𝜑𝜓))

Proof of Theorem pm2.54
StepHypRef Expression
1 df-or 383 . 2 ((𝜑𝜓) ↔ (¬ 𝜑𝜓))
21biimpri 216 1 ((¬ 𝜑𝜓) → (𝜑𝜓))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wo 381
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem depends on definitions:  df-bi 195  df-or 383
This theorem is referenced by:  orrd  391  tsbi3  32915
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