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Metamath Proof Explorer

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 )