Metamath Proof Explorer

Theorem pm2.85

Description: Theorem *2.85 of WhiteheadRussell p. 108. (Contributed by NM, 3-Jan-2005) (Proof shortened by Wolf Lammen, 5-Jan-2013)

Ref Expression
Assertion pm2.85 
|- ( ( ( ph \/ ps ) -> ( ph \/ ch ) ) -> ( ph \/ ( ps -> ch ) ) )

Proof

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