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Mirrors > Home > NFE Home > Th. List > notbi | Unicode version |
Description: Contraposition. Theorem *4.11 of [WhiteheadRussell] p. 117. (Contributed by NM, 21-May-1994.) (Proof shortened by Wolf Lammen, 12-Jun-2013.) |
Ref | Expression |
---|---|
notbi |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | id 19 | . . 3 | |
2 | 1 | notbid 285 | . 2 |
3 | id 19 | . . 3 | |
4 | 3 | con4bid 284 | . 2 |
5 | 2, 4 | impbii 180 | 1 |
Colors of variables: wff setvar class |
Syntax hints: wn 3 wb 176 |
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 177 |
This theorem is referenced by: notbii 287 con4bii 288 con2bi 318 nbn2 334 pm5.32 617 cbvexd 2009 rexxpf 4828 |
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