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Theorem onuni 4170
 Description: The union of an ordinal number is an ordinal number. (Contributed by NM, 29-Sep-2006.)
Assertion
Ref Expression
onuni (A On → A On)

Proof of Theorem onuni
StepHypRef Expression
1 onss 4169 . 2 (A On → A ⊆ On)
2 ssonuni 4164 . 2 (A On → (A ⊆ On → A On))
31, 2mpd 13 1 (A On → A On)
 Colors of variables: wff set class Syntax hints:   → wi 4   ∈ wcel 1374   ⊆ wss 2894  ∪ cuni 3554  Oncon0 4049 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-io 617  ax-5 1316  ax-7 1317  ax-gen 1318  ax-ie1 1363  ax-ie2 1364  ax-8 1376  ax-10 1377  ax-11 1378  ax-i12 1379  ax-bnd 1380  ax-4 1381  ax-13 1385  ax-14 1386  ax-17 1400  ax-i9 1404  ax-ial 1409  ax-i5r 1410  ax-ext 2004  ax-sep 3849  ax-un 4120 This theorem depends on definitions:  df-bi 110  df-3an 875  df-tru 1231  df-nf 1330  df-sb 1628  df-clab 2009  df-cleq 2015  df-clel 2018  df-nfc 2149  df-ral 2289  df-rex 2290  df-v 2537  df-in 2901  df-ss 2908  df-uni 3555  df-tr 3829  df-iord 4052  df-on 4054 This theorem is referenced by: (None)
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