Users' Mathboxes Mathbox for Richard Penner < Previous   Next >
Nearby theorems
Mirrors  >  Home  >  MPE Home  >  Th. List  >   Mathboxes  >  axfrege28 Structured version   Unicode version

Theorem axfrege28 37241
Description: Contraposition. Identical to con3 134.

Theorem *2.16 of [WhiteheadRussell] p. 103.

(Contributed by Richard Penner, 24-Dec-2019.)

Assertion
Ref Expression
axfrege28  |-  ( (
ph  ->  ps )  -> 
( -.  ps  ->  -. 
ph ) )

Proof of Theorem axfrege28
StepHypRef Expression
1 con3 134 1  |-  ( (
ph  ->  ps )  -> 
( -.  ps  ->  -. 
ph ) )
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    -> wi 4
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem is referenced by: (None)
  Copyright terms: Public domain W3C validator