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Theorem dmss 4534
 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 2939 . . . 4 (𝐴𝐵 → (⟨𝑥, 𝑦⟩ ∈ 𝐴 → ⟨𝑥, 𝑦⟩ ∈ 𝐵))
21eximdv 1760 . . 3 (𝐴𝐵 → (∃𝑦𝑥, 𝑦⟩ ∈ 𝐴 → ∃𝑦𝑥, 𝑦⟩ ∈ 𝐵))
3 vex 2560 . . . 4 𝑥 ∈ V
43eldm2 4533 . . 3 (𝑥 ∈ dom 𝐴 ↔ ∃𝑦𝑥, 𝑦⟩ ∈ 𝐴)
53eldm2 4533 . . 3 (𝑥 ∈ dom 𝐵 ↔ ∃𝑦𝑥, 𝑦⟩ ∈ 𝐵)
62, 4, 53imtr4g 194 . 2 (𝐴𝐵 → (𝑥 ∈ dom 𝐴𝑥 ∈ dom 𝐵))
76ssrdv 2951 1 (𝐴𝐵 → dom 𝐴 ⊆ dom 𝐵)
 Colors of variables: wff set class Syntax hints:   → wi 4  ∃wex 1381   ∈ wcel 1393   ⊆ wss 2917  ⟨cop 3378  dom cdm 4345 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-io 630  ax-5 1336  ax-7 1337  ax-gen 1338  ax-ie1 1382  ax-ie2 1383  ax-8 1395  ax-10 1396  ax-11 1397  ax-i12 1398  ax-bndl 1399  ax-4 1400  ax-17 1419  ax-i9 1423  ax-ial 1427  ax-i5r 1428  ax-ext 2022 This theorem depends on definitions:  df-bi 110  df-3an 887  df-tru 1246  df-nf 1350  df-sb 1646  df-clab 2027  df-cleq 2033  df-clel 2036  df-nfc 2167  df-v 2559  df-un 2922  df-in 2924  df-ss 2931  df-sn 3381  df-pr 3382  df-op 3384  df-br 3765  df-dm 4355 This theorem is referenced by:  dmeq  4535  dmv  4551  rnss  4564  dmiin  4580  ssxpbm  4756  ssxp1  4757  relrelss  4844  funssxp  5060  fvun1  5239  fndmdif  5272  fneqeql2  5276  tposss  5861  smores  5907  smores2  5909  tfrlemibfn  5942  tfrlemiubacc  5944  frecuzrdgfn  9198
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