Metamath Proof Explorer

Theorem orduniss

Description: An ordinal class includes its union. (Contributed by NM, 13-Sep-2003)

Ref Expression
Assertion orduniss 
|- ( Ord A -> U. A C_ A )

Proof

Step Hyp Ref Expression
1 ordtr 
 |-  ( Ord A -> Tr A )
2 df-tr 
 |-  ( Tr A <-> U. A C_ A )
3 1 2 sylib 
 |-  ( Ord A -> U. A C_ A )