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Theorem pm2.68 900
Description: Theorem *2.68 of [WhiteheadRussell] p. 108. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm2.68 (((𝜑𝜓) → 𝜓) → (𝜑𝜓))

Proof of Theorem pm2.68
StepHypRef Expression
1 jarl 125 . 2 (((𝜑𝜓) → 𝜓) → (¬ 𝜑𝜓))
21orrd 862 1 (((𝜑𝜓) → 𝜓) → (𝜑𝜓))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wo 846
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 210  df-or 847
This theorem is referenced by:  dfor2  901
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