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Mirrors > Home > ILE Home > Th. List > onun2i | GIF version |
Description: The union of two ordinal numbers is an ordinal number. (Contributed by NM, 13-Jun-1994.) (Constructive proof by Jim Kingdon, 25-Jul-2019.) |
Ref | Expression |
---|---|
onun2i.1 | ⊢ 𝐴 ∈ On |
onun2i.2 | ⊢ 𝐵 ∈ On |
Ref | Expression |
---|---|
onun2i | ⊢ (𝐴 ∪ 𝐵) ∈ On |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | onun2i.1 | . 2 ⊢ 𝐴 ∈ On | |
2 | onun2i.2 | . 2 ⊢ 𝐵 ∈ On | |
3 | onun2 4474 | . 2 ⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (𝐴 ∪ 𝐵) ∈ On) | |
4 | 1, 2, 3 | mp2an 424 | 1 ⊢ (𝐴 ∪ 𝐵) ∈ On |
Colors of variables: wff set class |
Syntax hints: ∈ wcel 2141 ∪ cun 3119 Oncon0 4348 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-io 704 ax-5 1440 ax-7 1441 ax-gen 1442 ax-ie1 1486 ax-ie2 1487 ax-8 1497 ax-10 1498 ax-11 1499 ax-i12 1500 ax-bndl 1502 ax-4 1503 ax-17 1519 ax-i9 1523 ax-ial 1527 ax-i5r 1528 ax-13 2143 ax-14 2144 ax-ext 2152 ax-sep 4107 ax-pr 4194 ax-un 4418 |
This theorem depends on definitions: df-bi 116 df-3an 975 df-tru 1351 df-nf 1454 df-sb 1756 df-clab 2157 df-cleq 2163 df-clel 2166 df-nfc 2301 df-ral 2453 df-rex 2454 df-v 2732 df-un 3125 df-in 3127 df-ss 3134 df-sn 3589 df-pr 3590 df-uni 3797 df-tr 4088 df-iord 4351 df-on 4353 |
This theorem is referenced by: (None) |
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