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Metamath Proof Explorer

Theorem pm3.11

Description: Theorem *3.11 of WhiteheadRussell p. 111. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm3.11 
|- ( -. ( -. ph \/ -. ps ) -> ( ph /\ ps ) )

Proof

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