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Theorem notnotd 570
Description: Deduction associated with notnot 569 and notnoti 584. (Contributed by Jarvin Udandy, 2-Sep-2016.) Avoid biconditional. (Revised by Wolf Lammen, 27-Mar-2021.)
Hypothesis
Ref Expression
notnotd.1  |-  ( ph  ->  ps )
Assertion
Ref Expression
notnotd  |-  ( ph  ->  -.  -.  ps )

Proof of Theorem notnotd
StepHypRef Expression
1 notnotd.1 . 2  |-  ( ph  ->  ps )
2 notnot 569 . 2  |-  ( ps 
->  -.  -.  ps )
31, 2syl 14 1  |-  ( 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-mp 7  ax-in1 554  ax-in2 555
This theorem is referenced by:  mod2eq1n2dvds  10191
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