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Metamath Proof Explorer

Theorem pm2.37

Description: Theorem *2.37 of WhiteheadRussell p. 105. (Contributed by NM, 6-Mar-2008)

Ref Expression
Assertion pm2.37 
|- ( ( ps -> ch ) -> ( ( ps \/ ph ) -> ( ph \/ ch ) ) )

Proof

Step Hyp Ref Expression
1 pm2.38 
 |-  ( ( ps -> ch ) -> ( ( ps \/ ph ) -> ( ch \/ ph ) ) )
2 pm1.4 
 |-  ( ( ch \/ ph ) -> ( ph \/ ch ) )
3 1 2 syl6 
 |-  ( ( ps -> ch ) -> ( ( ps \/ ph ) -> ( ph \/ ch ) ) )