Theorem orduni 4599

Description: The union of an ordinal class is ordinal. (Contributed by NM, 12-Sep-2003.)

Assertion

Ref	Expression
orduni	|- ( Ord A -> Ord U. A )

Proof of Theorem orduni

Step	Hyp	Ref	Expression
1		ordsson 4596	. 2 |- ( Ord A -> A C_ On )
2		ssorduni 4591	. 2 |- ( A C_ On -> Ord U. A )
3	1, 2	syl 14	1 |- ( Ord A -> Ord U. A )

Syntax hints:   -> wi 4   C_ wss 3201   U.cuni 3898   Ord word 4465   Oncon0 4466

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 717  ax-5 1496  ax-7 1497  ax-gen 1498  ax-ie1 1542  ax-ie2 1543  ax-8 1553  ax-10 1554  ax-11 1555  ax-i12 1556  ax-bndl 1558  ax-4 1559  ax-17 1575  ax-i9 1579  ax-ial 1583  ax-i5r 1584  ax-ext 2213

This theorem depends on definitions:  df-bi 117  df-3an 1007  df-tru 1401  df-nf 1510  df-sb 1811  df-clab 2218  df-cleq 2224  df-clel 2227  df-nfc 2364  df-ral 2516  df-rex 2517  df-v 2805  df-in 3207  df-ss 3214  df-uni 3899  df-tr 4193  df-iord 4469  df-on 4471

This theorem is referenced by:  tfrcl  6573