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Theorem pm2.01 157
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 150 1 |- ((ph -> -. ph) -> -. ph)
Colors of variables: wff set class
Syntax hints:  -. wn 3   -> wi 4
This theorem is referenced by:  bijustOLD 172  bijust 173  pm4.8 357  dtrucor2 3522  ominf 5904  elirr 6035  usinuniop 11155
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
Copyright terms: Public domain