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Mirrors > Home > MPE Home > Th. List > onfin | Structured version Visualization version GIF version |
Description: An ordinal number is finite iff it is a natural number. Proposition 10.32 of [TakeutiZaring] p. 92. (Contributed by NM, 26-Jul-2004.) |
Ref | Expression |
---|---|
onfin | ⊢ (𝐴 ∈ On → (𝐴 ∈ Fin ↔ 𝐴 ∈ ω)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | isfi 8764 | . 2 ⊢ (𝐴 ∈ Fin ↔ ∃𝑥 ∈ ω 𝐴 ≈ 𝑥) | |
2 | onomeneq 9011 | . . . . 5 ⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ ω) → (𝐴 ≈ 𝑥 ↔ 𝐴 = 𝑥)) | |
3 | eleq1a 2834 | . . . . . 6 ⊢ (𝑥 ∈ ω → (𝐴 = 𝑥 → 𝐴 ∈ ω)) | |
4 | 3 | adantl 482 | . . . . 5 ⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ ω) → (𝐴 = 𝑥 → 𝐴 ∈ ω)) |
5 | 2, 4 | sylbid 239 | . . . 4 ⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ ω) → (𝐴 ≈ 𝑥 → 𝐴 ∈ ω)) |
6 | 5 | rexlimdva 3213 | . . 3 ⊢ (𝐴 ∈ On → (∃𝑥 ∈ ω 𝐴 ≈ 𝑥 → 𝐴 ∈ ω)) |
7 | enrefnn 8837 | . . . 4 ⊢ (𝐴 ∈ ω → 𝐴 ≈ 𝐴) | |
8 | breq2 5078 | . . . . 5 ⊢ (𝑥 = 𝐴 → (𝐴 ≈ 𝑥 ↔ 𝐴 ≈ 𝐴)) | |
9 | 8 | rspcev 3561 | . . . 4 ⊢ ((𝐴 ∈ ω ∧ 𝐴 ≈ 𝐴) → ∃𝑥 ∈ ω 𝐴 ≈ 𝑥) |
10 | 7, 9 | mpdan 684 | . . 3 ⊢ (𝐴 ∈ ω → ∃𝑥 ∈ ω 𝐴 ≈ 𝑥) |
11 | 6, 10 | impbid1 224 | . 2 ⊢ (𝐴 ∈ On → (∃𝑥 ∈ ω 𝐴 ≈ 𝑥 ↔ 𝐴 ∈ ω)) |
12 | 1, 11 | bitrid 282 | 1 ⊢ (𝐴 ∈ On → (𝐴 ∈ Fin ↔ 𝐴 ∈ ω)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 205 ∧ wa 396 = wceq 1539 ∈ wcel 2106 ∃wrex 3065 class class class wbr 5074 Oncon0 6266 ωcom 7712 ≈ cen 8730 Fincfn 8733 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1798 ax-4 1812 ax-5 1913 ax-6 1971 ax-7 2011 ax-8 2108 ax-9 2116 ax-10 2137 ax-11 2154 ax-12 2171 ax-ext 2709 ax-sep 5223 ax-nul 5230 ax-pr 5352 ax-un 7588 |
This theorem depends on definitions: df-bi 206 df-an 397 df-or 845 df-3or 1087 df-3an 1088 df-tru 1542 df-fal 1552 df-ex 1783 df-nf 1787 df-sb 2068 df-mo 2540 df-eu 2569 df-clab 2716 df-cleq 2730 df-clel 2816 df-nfc 2889 df-ne 2944 df-ral 3069 df-rex 3070 df-reu 3072 df-rab 3073 df-v 3434 df-sbc 3717 df-csb 3833 df-dif 3890 df-un 3892 df-in 3894 df-ss 3904 df-pss 3906 df-nul 4257 df-if 4460 df-pw 4535 df-sn 4562 df-pr 4564 df-op 4568 df-uni 4840 df-br 5075 df-opab 5137 df-mpt 5158 df-tr 5192 df-id 5489 df-eprel 5495 df-po 5503 df-so 5504 df-fr 5544 df-we 5546 df-xp 5595 df-rel 5596 df-cnv 5597 df-co 5598 df-dm 5599 df-rn 5600 df-res 5601 df-ima 5602 df-ord 6269 df-on 6270 df-lim 6271 df-suc 6272 df-iota 6391 df-fun 6435 df-fn 6436 df-f 6437 df-f1 6438 df-fo 6439 df-f1o 6440 df-fv 6441 df-om 7713 df-1o 8297 df-en 8734 df-dom 8735 df-sdom 8736 df-fin 8737 |
This theorem is referenced by: onfin2 9014 fin17 10150 isfin7-2 10152 |
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