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Theorem pm2.45 899
Description: Theorem *2.45 of [WhiteheadRussell] p. 106. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm2.45 (¬ (𝜑𝜓) → ¬ 𝜑)

Proof of Theorem pm2.45
StepHypRef Expression
1 orc 847 . 2 (𝜑 → (𝜑𝜓))
21con3i 151 1 (¬ (𝜑𝜓) → ¬ 𝜑)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wo 826
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 197  df-or 827
This theorem is referenced by:  pm2.47  901  dn1  1044  eueq3  3531  outpasch  25867  acopyeu  25945  tgasa1  25959  unbdqndv2lem1  32831
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