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Theorem pm4.64 386
Description: Theorem *4.64 of [WhiteheadRussell] p. 120. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm4.64 ((¬ 𝜑𝜓) ↔ (𝜑𝜓))

Proof of Theorem pm4.64
StepHypRef Expression
1 df-or 384 . 2 ((𝜑𝜓) ↔ (¬ 𝜑𝜓))
21bicomi 213 1 ((¬ 𝜑𝜓) ↔ (𝜑𝜓))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wb 195  wo 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 196  df-or 384
This theorem is referenced by:  pm4.66  435  ioran  510  dfifp3  1009  dfnf5  3906  fimaxg  8092  fiming  8287  kmlem8  8862  axgroth6  9529  dfcon2  21032  ifpimimb  36868  ifpor123g  36872  hirstL-ax3  39708
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