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Theorem pm2.45 667
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 643 . 2 (𝜑 → (𝜑𝜓))
21con3i 572 1 (¬ (𝜑𝜓) → ¬ 𝜑)
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4  wo 639
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-in1 554  ax-in2 555  ax-io 640
This theorem depends on definitions:  df-bi 114
This theorem is referenced by:  pm2.47  669  ioran  679  dn1dc  878  eueq3dc  2738
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