Metamath Proof Explorer


Theorem conax1

Description: Contrapositive of ax-1 . (Contributed by BJ, 28-Oct-2023)

Ref Expression
Assertion conax1
|- ( -. ( ph -> ps ) -> -. ps )

Proof

Step Hyp Ref Expression
1 ax-1
 |-  ( ps -> ( ph -> ps ) )
2 1 con3i
 |-  ( -. ( ph -> ps ) -> -. ps )