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Theorem qsss1 38290
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 4053 . . 3 (𝐴𝐵 → (∃𝑥𝐴 𝑦 = [𝑥]𝐶 → ∃𝑥𝐵 𝑦 = [𝑥]𝐶))
21ss2abdv 4066 . 2 (𝐴𝐵 → {𝑦 ∣ ∃𝑥𝐴 𝑦 = [𝑥]𝐶} ⊆ {𝑦 ∣ ∃𝑥𝐵 𝑦 = [𝑥]𝐶})
3 df-qs 8751 . 2 (𝐴 / 𝐶) = {𝑦 ∣ ∃𝑥𝐴 𝑦 = [𝑥]𝐶}
4 df-qs 8751 . 2 (𝐵 / 𝐶) = {𝑦 ∣ ∃𝑥𝐵 𝑦 = [𝑥]𝐶}
52, 3, 43sstr4g 4037 1 (𝐴𝐵 → (𝐴 / 𝐶) ⊆ (𝐵 / 𝐶))
Colors of variables: wff setvar class
Syntax hints:  wi 4   = wceq 1540  {cab 2714  wrex 3070  wss 3951  [cec 8743   / cqs 8744
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1795  ax-4 1809  ax-5 1910  ax-6 1967  ax-7 2007  ax-9 2118  ax-ext 2708
This theorem depends on definitions:  df-bi 207  df-an 396  df-ex 1780  df-sb 2065  df-clab 2715  df-cleq 2729  df-rex 3071  df-ss 3968  df-qs 8751
This theorem is referenced by: (None)
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