Metamath Proof Explorer

Theorem pm2.31

Description: Theorem *2.31 of WhiteheadRussell p. 104. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm2.31 
|- ( ( ph \/ ( ps \/ ch ) ) -> ( ( ph \/ ps ) \/ ch ) )

Proof

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