Metamath Proof Explorer

Theorem pm4.53

Description: Theorem *4.53 of WhiteheadRussell p. 120. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm4.53 
|- ( -. ( ph /\ -. ps ) <-> ( -. ph \/ ps ) )

Proof

Step Hyp Ref Expression
1 pm4.52 
 |-  ( ( ph /\ -. ps ) <-> -. ( -. ph \/ ps ) )
2 1 con2bii 
 |-  ( ( -. ph \/ ps ) <-> -. ( ph /\ -. ps ) )
3 2 bicomi 
 |-  ( -. ( ph /\ -. ps ) <-> ( -. ph \/ ps ) )