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Theorem founiiun 45122
Description: Union expressed as an indexed union, when a map onto is given. (Contributed by Glauco Siliprandi, 17-Aug-2020.)
Assertion
Ref Expression
founiiun (𝐹:𝐴onto𝐵 𝐵 = 𝑥𝐴 (𝐹𝑥))
Distinct variable groups:   𝑥,𝐴   𝑥,𝐵   𝑥,𝐹

Proof of Theorem founiiun
Dummy variable 𝑦 is distinct from all other variables.
StepHypRef Expression
1 uniiun 5063 . 2 𝐵 = 𝑦𝐵 𝑦
2 foelcdmi 6970 . . . . . 6 ((𝐹:𝐴onto𝐵𝑦𝐵) → ∃𝑥𝐴 (𝐹𝑥) = 𝑦)
3 eqimss2 4055 . . . . . . 7 ((𝐹𝑥) = 𝑦𝑦 ⊆ (𝐹𝑥))
43reximi 3082 . . . . . 6 (∃𝑥𝐴 (𝐹𝑥) = 𝑦 → ∃𝑥𝐴 𝑦 ⊆ (𝐹𝑥))
52, 4syl 17 . . . . 5 ((𝐹:𝐴onto𝐵𝑦𝐵) → ∃𝑥𝐴 𝑦 ⊆ (𝐹𝑥))
65ralrimiva 3144 . . . 4 (𝐹:𝐴onto𝐵 → ∀𝑦𝐵𝑥𝐴 𝑦 ⊆ (𝐹𝑥))
7 iunss2 5054 . . . 4 (∀𝑦𝐵𝑥𝐴 𝑦 ⊆ (𝐹𝑥) → 𝑦𝐵 𝑦 𝑥𝐴 (𝐹𝑥))
86, 7syl 17 . . 3 (𝐹:𝐴onto𝐵 𝑦𝐵 𝑦 𝑥𝐴 (𝐹𝑥))
9 fof 6821 . . . . . . 7 (𝐹:𝐴onto𝐵𝐹:𝐴𝐵)
109ffvelcdmda 7104 . . . . . 6 ((𝐹:𝐴onto𝐵𝑥𝐴) → (𝐹𝑥) ∈ 𝐵)
11 ssidd 4019 . . . . . 6 ((𝐹:𝐴onto𝐵𝑥𝐴) → (𝐹𝑥) ⊆ (𝐹𝑥))
12 sseq2 4022 . . . . . . 7 (𝑦 = (𝐹𝑥) → ((𝐹𝑥) ⊆ 𝑦 ↔ (𝐹𝑥) ⊆ (𝐹𝑥)))
1312rspcev 3622 . . . . . 6 (((𝐹𝑥) ∈ 𝐵 ∧ (𝐹𝑥) ⊆ (𝐹𝑥)) → ∃𝑦𝐵 (𝐹𝑥) ⊆ 𝑦)
1410, 11, 13syl2anc 584 . . . . 5 ((𝐹:𝐴onto𝐵𝑥𝐴) → ∃𝑦𝐵 (𝐹𝑥) ⊆ 𝑦)
1514ralrimiva 3144 . . . 4 (𝐹:𝐴onto𝐵 → ∀𝑥𝐴𝑦𝐵 (𝐹𝑥) ⊆ 𝑦)
16 iunss2 5054 . . . 4 (∀𝑥𝐴𝑦𝐵 (𝐹𝑥) ⊆ 𝑦 𝑥𝐴 (𝐹𝑥) ⊆ 𝑦𝐵 𝑦)
1715, 16syl 17 . . 3 (𝐹:𝐴onto𝐵 𝑥𝐴 (𝐹𝑥) ⊆ 𝑦𝐵 𝑦)
188, 17eqssd 4013 . 2 (𝐹:𝐴onto𝐵 𝑦𝐵 𝑦 = 𝑥𝐴 (𝐹𝑥))
191, 18eqtrid 2787 1 (𝐹:𝐴onto𝐵 𝐵 = 𝑥𝐴 (𝐹𝑥))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wa 395   = wceq 1537  wcel 2106  wral 3059  wrex 3068  wss 3963   cuni 4912   ciun 4996  ontowfo 6561  cfv 6563
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1792  ax-4 1806  ax-5 1908  ax-6 1965  ax-7 2005  ax-8 2108  ax-9 2116  ax-10 2139  ax-11 2155  ax-12 2175  ax-ext 2706  ax-sep 5302  ax-nul 5312  ax-pr 5438
This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-3an 1088  df-tru 1540  df-fal 1550  df-ex 1777  df-nf 1781  df-sb 2063  df-mo 2538  df-eu 2567  df-clab 2713  df-cleq 2727  df-clel 2814  df-nfc 2890  df-ne 2939  df-ral 3060  df-rex 3069  df-rab 3434  df-v 3480  df-dif 3966  df-un 3968  df-ss 3980  df-nul 4340  df-if 4532  df-sn 4632  df-pr 4634  df-op 4638  df-uni 4913  df-iun 4998  df-br 5149  df-opab 5211  df-mpt 5232  df-id 5583  df-xp 5695  df-rel 5696  df-cnv 5697  df-co 5698  df-dm 5699  df-rn 5700  df-iota 6516  df-fun 6565  df-fn 6566  df-f 6567  df-fo 6569  df-fv 6571
This theorem is referenced by:  founiiun0  45133  issalnnd  46301  caragenunicl  46480  isomenndlem  46486
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