Metamath Proof Explorer

Theorem pm3.1

Description: Theorem *3.1 of WhiteheadRussell p. 111. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm3.1 
|- ( ( ph /\ ps ) -> -. ( -. ph \/ -. ps ) )

Proof

Step Hyp Ref Expression
1 anor 
 |-  ( ( ph /\ ps ) <-> -. ( -. ph \/ -. ps ) )
2 1 biimpi 
 |-  ( ( ph /\ ps ) -> -. ( -. ph \/ -. ps ) )