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Mirrors > Home > ILE Home > Th. List > notnotrdc | Unicode version |
Description: Double negation elimination for a decidable proposition. The converse, notnot 559, holds for all propositions, not just decidable ones. This is Theorem *2.14 of [WhiteheadRussell] p. 102, but with a decidability condition added. (Contributed by Jim Kingdon, 11-Mar-2018.) |
Ref | Expression |
---|---|
notnotrdc | DECID |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-dc 743 | . . 3 DECID | |
2 | orcom 647 | . . 3 | |
3 | 1, 2 | bitri 173 | . 2 DECID |
4 | pm2.53 641 | . 2 | |
5 | 3, 4 | sylbi 114 | 1 DECID |
Colors of variables: wff set class |
Syntax hints: wn 3 wi 4 wo 629 DECID wdc 742 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 99 ax-ia2 100 ax-ia3 101 ax-in2 545 ax-io 630 |
This theorem depends on definitions: df-bi 110 df-dc 743 |
This theorem is referenced by: dcimpstab 752 notnotbdc 766 condandc 775 pm2.13dc 779 pm2.54dc 790 |
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