Metamath Proof Explorer

Theorem pm4.77

Description: Theorem *4.77 of WhiteheadRussell p. 121. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm4.77 
|- ( ( ( ps -> ph ) /\ ( ch -> ph ) ) <-> ( ( ps \/ ch ) -> ph ) )

Proof

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