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Theorem biortn 746
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 notnot 630 . 2  |-  ( ph  ->  -.  -.  ph )
2 biorf 745 . 2  |-  ( -. 
-.  ph  ->  ( ps  <->  ( -.  ph  \/  ps ) ) )
31, 2syl 14 1  |-  ( ph  ->  ( ps  <->  ( -.  ph  \/  ps ) ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    <-> wb 105    \/ wo 709
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 615  ax-in2 616  ax-io 710
This theorem depends on definitions:  df-bi 117
This theorem is referenced by:  oranabs  816
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