Metamath Proof Explorer

Theorem pm2.45

Description: Theorem *2.45 of WhiteheadRussell p. 106. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm2.45 
|- ( -. ( ph \/ ps ) -> -. ph )

Proof

Step Hyp Ref Expression
1 orc 
 |-  ( ph -> ( ph \/ ps ) )
2 1 con3i 
 |-  ( -. ( ph \/ ps ) -> -. ph )