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Theorem pm4.66dc 871
Description: Theorem *4.66 of [WhiteheadRussell] p. 120, given a decidability condition. (Contributed by Jim Kingdon, 2-May-2018.)
Assertion
Ref Expression
pm4.66dc  |-  (DECID  ph  ->  ( ( -.  ph  ->  -. 
ps )  <->  ( ph  \/  -.  ps ) ) )

Proof of Theorem pm4.66dc
StepHypRef Expression
1 pm4.64dc 870 1  |-  (DECID  ph  ->  ( ( -.  ph  ->  -. 
ps )  <->  ( ph  \/  -.  ps ) ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    <-> wb 104    \/ wo 682  DECID wdc 804
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 588  ax-in2 589  ax-io 683
This theorem depends on definitions:  df-bi 116  df-dc 805
This theorem is referenced by:  pm4.54dc  872
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