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Theorem pm2.45 656
Description: Theorem *2.45 of [WhiteheadRussell] p. 106. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm2.45 (¬ (φ ψ) → ¬ φ)

Proof of Theorem pm2.45
StepHypRef Expression
1 orc 632 . 2 (φ → (φ ψ))
21con3i 561 1 (¬ (φ ψ) → ¬ φ)
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4   wo 628
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-in1 544  ax-in2 545  ax-io 629
This theorem depends on definitions:  df-bi 110
This theorem is referenced by:  pm2.47  658  ioran  668  dn1dc  866  eueq3dc  2709
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