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Theorem ssct 9002
Description: Any subset of a countable set is countable. (Contributed by Thierry Arnoux, 31-Jan-2017.) Avoid ax-pow 5325, ax-un 7677. (Revised by BTernaryTau, 7-Dec-2024.)
Assertion
Ref Expression
ssct ((𝐴𝐵𝐵 ≼ ω) → 𝐴 ≼ ω)

Proof of Theorem ssct
StepHypRef Expression
1 domssl 8945 1 ((𝐴𝐵𝐵 ≼ ω) → 𝐴 ≼ ω)
Colors of variables: wff setvar class
Syntax hints:  wi 4  wa 397  wss 3915   class class class wbr 5110  ωcom 7807  cdom 8888
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 1914  ax-6 1972  ax-7 2012  ax-8 2109  ax-9 2117  ax-ext 2708  ax-sep 5261  ax-nul 5268  ax-pr 5389
This theorem depends on definitions:  df-bi 206  df-an 398  df-or 847  df-3an 1090  df-tru 1545  df-fal 1555  df-ex 1783  df-sb 2069  df-clab 2715  df-cleq 2729  df-clel 2815  df-ral 3066  df-rex 3075  df-rab 3411  df-v 3450  df-dif 3918  df-un 3920  df-in 3922  df-ss 3932  df-nul 4288  df-if 4492  df-sn 4592  df-pr 4594  df-op 4598  df-br 5111  df-opab 5173  df-xp 5644  df-rel 5645  df-cnv 5646  df-co 5647  df-dm 5648  df-rn 5649  df-res 5650  df-fun 6503  df-fn 6504  df-f 6505  df-f1 6506  df-dom 8892
This theorem is referenced by:  measvuni  32853  measiuns  32856  sxbrsigalem1  32925  ssnct  43361  fzct  43687  fzoct  43692  salexct  44649  opnvonmbllem2  44948
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