Metamath Proof Explorer

Theorem pm4.65

Description: Theorem *4.65 of WhiteheadRussell p. 120. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm4.65 
|- ( -. ( -. ph -> ps ) <-> ( -. ph /\ -. ps ) )

Proof

Step Hyp Ref Expression
1 pm4.61 
 |-  ( -. ( -. ph -> ps ) <-> ( -. ph /\ -. ps ) )