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Theorem con3 134
Description: Contraposition. Theorem *2.16 of [WhiteheadRussell] p. 103. This was the fourth axiom of Frege, specifically Proposition 28 of [Frege1879] p. 43. (Contributed by NM, 29-Dec-1992.) (Proof shortened by Wolf Lammen, 13-Feb-2013.)
Assertion
Ref Expression
con3

Proof of Theorem con3
StepHypRef Expression
1 id 22 . 2
21con3d 133 1
Colors of variables: wff setvar class
Syntax hints:  -.wn 3  ->wi 4
This theorem is referenced by:  pm2.65  172  con34b  292  nic-ax  1481  nic-axALT  1482  eximOLD  1625  axc10  1960  ax12indn  2253  rexim  2928  ralf0  3900  dfon2lem9  28060  hbntg  28075  naim1  28687  naim2  28688  lukshef-ax2  28717  vk15.4j  32076  tratrb  32085  hbntal  32105  tratrbVD  32440  con5VD  32479  vk15.4jVD  32493  bj-axc10v  33058  cvrexchlem  33914  cvratlem  33916  axfrege28  36529  bj-frege52a  36557
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
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