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Theorem pm2.18 110
Description: Proof by contradiction. Theorem *2.18 of [WhiteheadRussell] p. 103. Also called the Law of Clavius. See also pm2.01 168. (Contributed by NM, 29-Dec-1992.)
Assertion
Ref Expression
pm2.18

Proof of Theorem pm2.18
StepHypRef Expression
1 pm2.21 108 . . . 4
21a2i 13 . . 3
32con4d 105 . 2
43pm2.43i 47 1
Colors of variables: wff setvar class
Syntax hints:  -.wn 3  ->wi 4
This theorem is referenced by:  pm2.18d  111  pm4.81  366  sumdmdlem2  27338  pm4.81ALT  34136  bj-pm2.18i  34141
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
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