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Theorem notnot2ALT2 28748
Description: Converse of double negation. Theorem *2.14 of [WhiteheadRussell] p. 102. Proof derived by completeusersproof.c from User's Proof in VirtualDeductionProofs.txt. (Contributed by Alan Sare, 11-Sep-2016.)
Assertion
Ref Expression
notnot2ALT2  |-  ( -. 
-.  ph  ->  ph )

Proof of Theorem notnot2ALT2
StepHypRef Expression
1 notnot2 106 1  |-  ( -. 
-.  ph  ->  ph )
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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