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Theorem notbi 286
Description: Contraposition. Theorem *4.11 of [WhiteheadRussell] p. 117. (Contributed by NM, 21-May-1994.) (Proof shortened by Wolf Lammen, 12-Jun-2013.)
Assertion
Ref Expression
notbi

Proof of Theorem notbi
StepHypRef Expression
1 id 19 . . 3
21notbid 285 . 2
3 id 19 . . 3
43con4bid 284 . 2
52, 4impbii 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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