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Theorem dmss 4561
Description: Subset theorem for domain. (Contributed by NM, 11-Aug-1994.)
Assertion
Ref Expression
dmss (𝐴𝐵 → dom 𝐴 ⊆ dom 𝐵)

Proof of Theorem dmss
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 ssel 2966 . . . 4 (𝐴𝐵 → (⟨𝑥, 𝑦⟩ ∈ 𝐴 → ⟨𝑥, 𝑦⟩ ∈ 𝐵))
21eximdv 1776 . . 3 (𝐴𝐵 → (∃𝑦𝑥, 𝑦⟩ ∈ 𝐴 → ∃𝑦𝑥, 𝑦⟩ ∈ 𝐵))
3 vex 2577 . . . 4 𝑥 ∈ V
43eldm2 4560 . . 3 (𝑥 ∈ dom 𝐴 ↔ ∃𝑦𝑥, 𝑦⟩ ∈ 𝐴)
53eldm2 4560 . . 3 (𝑥 ∈ dom 𝐵 ↔ ∃𝑦𝑥, 𝑦⟩ ∈ 𝐵)
62, 4, 53imtr4g 198 . 2 (𝐴𝐵 → (𝑥 ∈ dom 𝐴𝑥 ∈ dom 𝐵))
76ssrdv 2978 1 (𝐴𝐵 → dom 𝐴 ⊆ dom 𝐵)
Colors of variables: wff set class
Syntax hints:  wi 4  wex 1397  wcel 1409  wss 2944  cop 3405  dom cdm 4372
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-ia2 104  ax-ia3 105  ax-io 640  ax-5 1352  ax-7 1353  ax-gen 1354  ax-ie1 1398  ax-ie2 1399  ax-8 1411  ax-10 1412  ax-11 1413  ax-i12 1414  ax-bndl 1415  ax-4 1416  ax-17 1435  ax-i9 1439  ax-ial 1443  ax-i5r 1444  ax-ext 2038
This theorem depends on definitions:  df-bi 114  df-3an 898  df-tru 1262  df-nf 1366  df-sb 1662  df-clab 2043  df-cleq 2049  df-clel 2052  df-nfc 2183  df-v 2576  df-un 2949  df-in 2951  df-ss 2958  df-sn 3408  df-pr 3409  df-op 3411  df-br 3792  df-dm 4382
This theorem is referenced by:  dmeq  4562  dmv  4578  rnss  4591  dmiin  4607  ssxpbm  4783  ssxp1  4784  relrelss  4871  funssxp  5087  fvun1  5266  fndmdif  5299  fneqeql2  5303  tposss  5891  smores  5937  smores2  5939  tfrlemibfn  5972  tfrlemiubacc  5974  frecuzrdgfn  9361
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