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Theorem biortn 395
Description: A wff is equivalent to its negated disjunction with falsehood. (Contributed by NM, 9-Jul-2012.)
Assertion
Ref Expression
biortn  |-  ( ph  ->  ( ps  <->  ( -.  ph  \/  ps ) ) )

Proof of Theorem biortn
StepHypRef Expression
1 notnot1 114 . 2  |-  ( ph  ->  -.  -.  ph )
2 biorf 394 . 2  |-  ( -. 
-.  ph  ->  ( ps  <->  ( -.  ph  \/  ps ) ) )
31, 2syl 15 1  |-  ( ph  ->  ( ps  <->  ( -.  ph  \/  ps ) ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    <-> wb 176    \/ wo 357
This theorem is referenced by:  oranabs  829  ballotlemfc0  23051  ballotlemfcc  23052  xrdifh  23273  4atlem3a  29786  4atlem3b  29787
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 177  df-or 359
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