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Theorem pm3.13 1008
Description: Theorem *3.13 of [WhiteheadRussell] p. 111. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm3.13 (¬ (𝜑𝜓) → (¬ 𝜑 ∨ ¬ 𝜓))

Proof of Theorem pm3.13
StepHypRef Expression
1 pm3.11 1006 . 2 (¬ (¬ 𝜑 ∨ ¬ 𝜓) → (𝜑𝜓))
21con1i 146 1 (¬ (𝜑𝜓) → (¬ 𝜑 ∨ ¬ 𝜓))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wa 384  wo 865
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 198  df-an 385  df-or 866
This theorem is referenced by:  ifcomnan  4330  suc11  6041  naim1  32702  naim2  32703  tsbi1  34247  vk15.4j  39229  vk15.4jVD  39641
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