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Metamath Proof Explorer

Theorem pm2.48

Description: Theorem *2.48 of WhiteheadRussell p. 107. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm2.48 
|- ( -. ( ph \/ ps ) -> ( ph \/ -. ps ) )

Proof

Step Hyp Ref Expression
1 pm2.46 
 |-  ( -. ( ph \/ ps ) -> -. ps )
2 1 olcd 
 |-  ( -. ( ph \/ ps ) -> ( ph \/ -. ps ) )