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Mirrors > Home > MPE Home > Th. List > notnotb | Structured version Visualization version GIF version |
Description: Double negation. Theorem *4.13 of [WhiteheadRussell] p. 117. (Contributed by NM, 3-Jan-1993.) |
Ref | Expression |
---|---|
notnotb | ⊢ (𝜑 ↔ ¬ ¬ 𝜑) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | notnot 135 | . 2 ⊢ (𝜑 → ¬ ¬ 𝜑) | |
2 | notnotr 124 | . 2 ⊢ (¬ ¬ 𝜑 → 𝜑) | |
3 | 1, 2 | impbii 198 | 1 ⊢ (𝜑 ↔ ¬ ¬ 𝜑) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 ↔ wb 195 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 |
This theorem depends on definitions: df-bi 196 |
This theorem is referenced by: notnotdOLD 304 notbid 307 con2bi 342 con1bii 345 imor 427 iman 439 dfbi3 933 ifpn 1016 alex 1743 necon1abid 2820 necon4abid 2822 necon2abid 2824 necon2bbid 2825 necon1abii 2830 dfral2 2977 ralnex2 3027 ralnex3 3028 elsymdifxor 3812 difsnpss 4279 xpimasn 5498 2mpt20 6780 bropfvvvv 7144 zfregs2 8492 nqereu 9630 ssnn0fi 12646 zeo4 14900 sumodd 14949 ncoprmlnprm 15274 wlkcpr 26057 vdn0frgrav2 26550 vdgn0frgrav2 26551 ballotlemfc0 29881 ballotlemfcc 29882 bnj1143 30115 bnj1304 30144 bnj1189 30331 bj-nfn 31795 wl-nfnbi 32493 tsim1 33107 tsna1 33121 ifpxorcor 36840 ifpnot23b 36846 ifpnot23c 36848 ifpnot23d 36849 iunrelexp0 37013 dfss6 37082 con5VD 38158 sineq0ALT 38195 jcn 38228 nepnfltpnf 38499 nemnftgtmnft 38501 sge0gtfsumgt 39336 atbiffatnnb 39728 falseral0 40308 islininds2 42067 nnolog2flm1 42182 |
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