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Metamath Proof Explorer

Theorem pm2.67-2

Description: Slight generalization of Theorem *2.67 of WhiteheadRussell p. 107. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm2.67-2 
|- ( ( ( ph \/ ch ) -> ps ) -> ( ph -> ps ) )

Proof

Step Hyp Ref Expression
1 orc 
 |-  ( ph -> ( ph \/ ch ) )
2 1 imim1i 
 |-  ( ( ( ph \/ ch ) -> ps ) -> ( ph -> ps ) )