Metamath Proof Explorer

Theorem pm4.61

Description: Theorem *4.61 of WhiteheadRussell p. 120. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm4.61 
|- ( -. ( ph -> ps ) <-> ( ph /\ -. ps ) )

Proof

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