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Theorem pm2.01 181
Description: Reductio ad absurdum. Theorem *2.01 of [WhiteheadRussell] p. 100. (The proof was shortened by O'Cat, 21-Nov-2008.) (The proof was shortened by Wolf Lammen, 31-Oct-2012.)
Assertion
Ref Expression
pm2.01 |- ((ph -> -. ph) -> -. ph)

Proof of Theorem pm2.01
StepHypRef Expression
1 id 18 . 2 |- (-. ph -> -. ph)
21, 1ja 172 1 |- ((ph -> -. ph) -> -. ph)
Colors of variables: wff set class
Syntax hints:  -. wn 2   -> wi 3
This theorem is referenced by:  pm2.01dOLD 183  bijustOLD 207  bijust 208  pm4.8 414  dtrucor2 3674  ominf 5992  elirr 6108  ruclem39 9772  usinuniop 11820
This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7
Copyright terms: Public domain