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Theorem pm3.11 486
Description: Theorem *3.11 of [WhiteheadRussell] p. 111. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm3.11  |-  ( -.  ( -.  ph  \/  -.  ps )  ->  ( ph  /\  ps ) )

Proof of Theorem pm3.11
StepHypRef Expression
1 anor 476 . 2  |-  ( (
ph  /\  ps )  <->  -.  ( -.  ph  \/  -.  ps ) )
21biimpri 198 1  |-  ( -.  ( -.  ph  \/  -.  ps )  ->  ( ph  /\  ps ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    \/ wo 358    /\ wa 359
This theorem is referenced by:  pm3.12  487  pm3.13  488  ecased  911
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
This theorem depends on definitions:  df-bi 178  df-or 360  df-an 361
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