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Theorem atbiffatnnbalt 27883
Description: If a implies b, it is implied a implies not not b (Contributed by Jarvin Udandy, 29-Aug-2016.)
Assertion
Ref Expression
atbiffatnnbalt  |-  ( (
ph  ->  ps )  -> 
( ph  ->  -.  -.  ps ) )

Proof of Theorem atbiffatnnbalt
StepHypRef Expression
1 notnot1 114 . 2  |-  ( ps 
->  -.  -.  ps )
21imim2i 13 1  |-  ( (
ph  ->  ps )  -> 
( ph  ->  -.  -.  ps ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
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