Metamath Proof Explorer

Theorem pm3.13

Description: Theorem *3.13 of WhiteheadRussell p. 111. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm3.13 
|- ( -. ( ph /\ ps ) -> ( -. ph \/ -. ps ) )

Proof

Step Hyp Ref Expression
1 pm3.11 
 |-  ( -. ( -. ph \/ -. ps ) -> ( ph /\ ps ) )
2 1 con1i 
 |-  ( -. ( ph /\ ps ) -> ( -. ph \/ -. ps ) )