Theorem 3orit

Description: Closed form of 3ori . (Contributed by Scott Fenton, 20-Apr-2011)

	Ref	Expression
Assertion	3orit	|- ( ( ph \/ ps \/ ch ) <-> ( ( -. ph /\ -. ps ) -> ch ) )

Proof

Step	Hyp	Ref	Expression
1		df-3or	|- ( ( ph \/ ps \/ ch ) <-> ( ( ph \/ ps ) \/ ch ) )
2		df-or	|- ( ( ( ph \/ ps ) \/ ch ) <-> ( -. ( ph \/ ps ) -> ch ) )
3		ioran	|- ( -. ( ph \/ ps ) <-> ( -. ph /\ -. ps ) )
4	3	imbi1i	|- ( ( -. ( ph \/ ps ) -> ch ) <-> ( ( -. ph /\ -. ps ) -> ch ) )
5	1 2 4	3bitri	|- ( ( ph \/ ps \/ ch ) <-> ( ( -. ph /\ -. ps ) -> ch ) )