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Theorem qsss1 34488
 Description: Subclass theorem for quotient sets. (Contributed by Peter Mazsa, 12-Sep-2020.)
Assertion
Ref Expression
qsss1 (𝐴𝐵 → (𝐴 / 𝐶) ⊆ (𝐵 / 𝐶))

Proof of Theorem qsss1
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 ssrexv 3829 . . 3 (𝐴𝐵 → (∃𝑥𝐴 𝑦 = [𝑥]𝐶 → ∃𝑥𝐵 𝑦 = [𝑥]𝐶))
21ss2abdv 3837 . 2 (𝐴𝐵 → {𝑦 ∣ ∃𝑥𝐴 𝑦 = [𝑥]𝐶} ⊆ {𝑦 ∣ ∃𝑥𝐵 𝑦 = [𝑥]𝐶})
3 df-qs 7955 . 2 (𝐴 / 𝐶) = {𝑦 ∣ ∃𝑥𝐴 𝑦 = [𝑥]𝐶}
4 df-qs 7955 . 2 (𝐵 / 𝐶) = {𝑦 ∣ ∃𝑥𝐵 𝑦 = [𝑥]𝐶}
52, 3, 43sstr4g 3808 1 (𝐴𝐵 → (𝐴 / 𝐶) ⊆ (𝐵 / 𝐶))
 Colors of variables: wff setvar class Syntax hints:   → wi 4   = wceq 1652  {cab 2751  ∃wrex 3056   ⊆ wss 3734  [cec 7947   / cqs 7948 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1890  ax-4 1904  ax-5 2005  ax-6 2070  ax-7 2105  ax-9 2164  ax-10 2183  ax-11 2198  ax-12 2211  ax-13 2352  ax-ext 2743 This theorem depends on definitions:  df-bi 198  df-an 385  df-or 874  df-tru 1656  df-ex 1875  df-nf 1879  df-sb 2063  df-clab 2752  df-cleq 2758  df-clel 2761  df-nfc 2896  df-rex 3061  df-in 3741  df-ss 3748  df-qs 7955 This theorem is referenced by: (None)
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