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Theorem nbn3 337
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 115 . 2  |-  -.  -.  ph
32nbn 336 1  |-  ( -. 
ps 
<->  ( ps  <->  -.  ph )
)
Colors of variables: wff set class
Syntax hints:   -. wn 3    <-> wb 176
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
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