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Theorem nbn3 690
Description: Transfer falsehood via equivalence. (Contributed by NM, 11-Sep-2006.)
Hypothesis
Ref Expression
nbn3.1  |-  ph
Assertion
Ref Expression
nbn3  |-  ( -. 
ps 
<->  ( ps  <->  -.  ph )
)

Proof of Theorem nbn3
StepHypRef Expression
1 nbn3.1 . . 3  |-  ph
21notnoti 635 . 2  |-  -.  -.  ph
32nbn 689 1  |-  ( -. 
ps 
<->  ( ps  <->  -.  ph )
)
Colors of variables: wff set class
Syntax hints:   -. wn 3    <-> wb 104
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 604  ax-in2 605
This theorem depends on definitions:  df-bi 116
This theorem is referenced by: (None)
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