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Mirrors > Home > ILE Home > Th. List > trssord | GIF version |
Description: A transitive subclass of an ordinal class is ordinal. (Contributed by NM, 29-May-1994.) |
Ref | Expression |
---|---|
trssord | ⊢ ((Tr 𝐴 ∧ 𝐴 ⊆ 𝐵 ∧ Ord 𝐵) → Ord 𝐴) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | dford3 4363 | . . . . . . 7 ⊢ (Ord 𝐵 ↔ (Tr 𝐵 ∧ ∀𝑥 ∈ 𝐵 Tr 𝑥)) | |
2 | 1 | simprbi 275 | . . . . . 6 ⊢ (Ord 𝐵 → ∀𝑥 ∈ 𝐵 Tr 𝑥) |
3 | ssralv 3219 | . . . . . 6 ⊢ (𝐴 ⊆ 𝐵 → (∀𝑥 ∈ 𝐵 Tr 𝑥 → ∀𝑥 ∈ 𝐴 Tr 𝑥)) | |
4 | 2, 3 | syl5 32 | . . . . 5 ⊢ (𝐴 ⊆ 𝐵 → (Ord 𝐵 → ∀𝑥 ∈ 𝐴 Tr 𝑥)) |
5 | 4 | imp 124 | . . . 4 ⊢ ((𝐴 ⊆ 𝐵 ∧ Ord 𝐵) → ∀𝑥 ∈ 𝐴 Tr 𝑥) |
6 | 5 | anim2i 342 | . . 3 ⊢ ((Tr 𝐴 ∧ (𝐴 ⊆ 𝐵 ∧ Ord 𝐵)) → (Tr 𝐴 ∧ ∀𝑥 ∈ 𝐴 Tr 𝑥)) |
7 | 6 | 3impb 1199 | . 2 ⊢ ((Tr 𝐴 ∧ 𝐴 ⊆ 𝐵 ∧ Ord 𝐵) → (Tr 𝐴 ∧ ∀𝑥 ∈ 𝐴 Tr 𝑥)) |
8 | dford3 4363 | . 2 ⊢ (Ord 𝐴 ↔ (Tr 𝐴 ∧ ∀𝑥 ∈ 𝐴 Tr 𝑥)) | |
9 | 7, 8 | sylibr 134 | 1 ⊢ ((Tr 𝐴 ∧ 𝐴 ⊆ 𝐵 ∧ Ord 𝐵) → Ord 𝐴) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 104 ∧ w3a 978 ∀wral 2455 ⊆ wss 3129 Tr wtr 4098 Ord word 4358 |
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-5 1447 ax-7 1448 ax-gen 1449 ax-ie1 1493 ax-ie2 1494 ax-8 1504 ax-11 1506 ax-4 1510 ax-17 1526 ax-i9 1530 ax-ial 1534 ax-i5r 1535 ax-ext 2159 |
This theorem depends on definitions: df-bi 117 df-3an 980 df-nf 1461 df-sb 1763 df-clab 2164 df-cleq 2170 df-clel 2173 df-ral 2460 df-in 3135 df-ss 3142 df-iord 4362 |
This theorem is referenced by: ordelord 4377 ordin 4381 ssorduni 4482 ordtriexmidlem 4514 ordtri2or2exmidlem 4521 onsucelsucexmidlem 4524 ordsuc 4558 |
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