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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 8526 | . . . 4 ⊢ (𝐵 ≼ ω → 𝐵 ∈ V) | |
2 | ssdomg 8557 | . . . 4 ⊢ (𝐵 ∈ V → (𝐴 ⊆ 𝐵 → 𝐴 ≼ 𝐵)) | |
3 | 1, 2 | syl 17 | . . 3 ⊢ (𝐵 ≼ ω → (𝐴 ⊆ 𝐵 → 𝐴 ≼ 𝐵)) |
4 | 3 | impcom 410 | . 2 ⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐵 ≼ ω) → 𝐴 ≼ 𝐵) |
5 | domtr 8564 | . 2 ⊢ ((𝐴 ≼ 𝐵 ∧ 𝐵 ≼ ω) → 𝐴 ≼ ω) | |
6 | 4, 5 | sylancom 590 | 1 ⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐵 ≼ ω) → 𝐴 ≼ ω) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 398 ∈ wcel 2114 Vcvv 3496 ⊆ wss 3938 class class class wbr 5068 ωcom 7582 ≼ cdom 8509 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1796 ax-4 1810 ax-5 1911 ax-6 1970 ax-7 2015 ax-8 2116 ax-9 2124 ax-10 2145 ax-11 2161 ax-12 2177 ax-ext 2795 ax-sep 5205 ax-nul 5212 ax-pow 5268 ax-pr 5332 ax-un 7463 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-3an 1085 df-tru 1540 df-ex 1781 df-nf 1785 df-sb 2070 df-mo 2622 df-eu 2654 df-clab 2802 df-cleq 2816 df-clel 2895 df-nfc 2965 df-ral 3145 df-rex 3146 df-rab 3149 df-v 3498 df-dif 3941 df-un 3943 df-in 3945 df-ss 3954 df-nul 4294 df-if 4470 df-pw 4543 df-sn 4570 df-pr 4572 df-op 4576 df-uni 4841 df-br 5069 df-opab 5131 df-id 5462 df-xp 5563 df-rel 5564 df-cnv 5565 df-co 5566 df-dm 5567 df-rn 5568 df-res 5569 df-ima 5570 df-fun 6359 df-fn 6360 df-f 6361 df-f1 6362 df-fo 6363 df-f1o 6364 df-dom 8513 |
This theorem is referenced by: measvuni 31475 measiuns 31478 sxbrsigalem1 31545 ssnct 41348 fzct 41655 fzoct 41661 salexct 42624 opnvonmbllem2 42922 |
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