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Mirrors > Home > MPE Home > Th. List > ssct | Structured version Visualization version GIF version |
Description: Any subset of a countable set is countable. (Contributed by Thierry Arnoux, 31-Jan-2017.) |
Ref | Expression |
---|---|
ssct | ⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐵 ≼ ω) → 𝐴 ≼ ω) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ctex 8507 | . . . 4 ⊢ (𝐵 ≼ ω → 𝐵 ∈ V) | |
2 | ssdomg 8538 | . . . 4 ⊢ (𝐵 ∈ V → (𝐴 ⊆ 𝐵 → 𝐴 ≼ 𝐵)) | |
3 | 1, 2 | syl 17 | . . 3 ⊢ (𝐵 ≼ ω → (𝐴 ⊆ 𝐵 → 𝐴 ≼ 𝐵)) |
4 | 3 | impcom 411 | . 2 ⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐵 ≼ ω) → 𝐴 ≼ 𝐵) |
5 | domtr 8545 | . 2 ⊢ ((𝐴 ≼ 𝐵 ∧ 𝐵 ≼ ω) → 𝐴 ≼ ω) | |
6 | 4, 5 | sylancom 591 | 1 ⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐵 ≼ ω) → 𝐴 ≼ ω) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 399 ∈ wcel 2111 Vcvv 3441 ⊆ wss 3881 class class class wbr 5030 ωcom 7560 ≼ cdom 8490 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1797 ax-4 1811 ax-5 1911 ax-6 1970 ax-7 2015 ax-8 2113 ax-9 2121 ax-10 2142 ax-11 2158 ax-12 2175 ax-ext 2770 ax-sep 5167 ax-nul 5174 ax-pow 5231 ax-pr 5295 ax-un 7441 |
This theorem depends on definitions: df-bi 210 df-an 400 df-or 845 df-3an 1086 df-tru 1541 df-ex 1782 df-nf 1786 df-sb 2070 df-mo 2598 df-eu 2629 df-clab 2777 df-cleq 2791 df-clel 2870 df-nfc 2938 df-ral 3111 df-rex 3112 df-rab 3115 df-v 3443 df-dif 3884 df-un 3886 df-in 3888 df-ss 3898 df-nul 4244 df-if 4426 df-pw 4499 df-sn 4526 df-pr 4528 df-op 4532 df-uni 4801 df-br 5031 df-opab 5093 df-id 5425 df-xp 5525 df-rel 5526 df-cnv 5527 df-co 5528 df-dm 5529 df-rn 5530 df-res 5531 df-ima 5532 df-fun 6326 df-fn 6327 df-f 6328 df-f1 6329 df-fo 6330 df-f1o 6331 df-dom 8494 |
This theorem is referenced by: measvuni 31583 measiuns 31586 sxbrsigalem1 31653 ssnct 41713 fzct 42012 fzoct 42018 salexct 42974 opnvonmbllem2 43272 |
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