Theorem ordtr

Description: An ordinal class is transitive. (Contributed by NM, 3-Apr-1994)

	Ref	Expression
Assertion	ordtr	|- ( Ord A -> Tr A )

Proof

Step	Hyp	Ref	Expression
1		df-ord	|- ( Ord A <-> ( Tr A /\ _E We A ) )
2	1	simplbi	|- ( Ord A -> Tr A )