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Theorem pm3.13 520
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 pm3.11 518 . 2 (¬ (¬ 𝜑 ∨ ¬ 𝜓) → (𝜑𝜓))
21con1i 142 1 (¬ (𝜑𝜓) → (¬ 𝜑 ∨ ¬ 𝜓))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wo 381  wa 382
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 195  df-or 383  df-an 384
This theorem is referenced by:  ifcomnan  4082  suc11  5730  naim1  31356  naim2  31357  tsbi1  32909  vk15.4j  37554  vk15.4jVD  37971
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