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Theorem iununi 4994
Description: A relationship involving union and indexed union. Exercise 25 of [Enderton] p. 33. (Contributed by NM, 25-Nov-2003.) (Proof shortened by Mario Carneiro, 17-Nov-2016.)
Assertion
Ref Expression
iununi ((𝐵 = ∅ → 𝐴 = ∅) ↔ (𝐴 𝐵) = 𝑥𝐵 (𝐴𝑥))
Distinct variable groups:   𝑥,𝐴   𝑥,𝐵

Proof of Theorem iununi
StepHypRef Expression
1 df-ne 2936 . . . . . . 7 (𝐵 ≠ ∅ ↔ ¬ 𝐵 = ∅)
2 iunconst 4900 . . . . . . 7 (𝐵 ≠ ∅ → 𝑥𝐵 𝐴 = 𝐴)
31, 2sylbir 238 . . . . . 6 𝐵 = ∅ → 𝑥𝐵 𝐴 = 𝐴)
4 iun0 4957 . . . . . . 7 𝑥𝐵 ∅ = ∅
5 id 22 . . . . . . . 8 (𝐴 = ∅ → 𝐴 = ∅)
65iuneq2d 4920 . . . . . . 7 (𝐴 = ∅ → 𝑥𝐵 𝐴 = 𝑥𝐵 ∅)
74, 6, 53eqtr4a 2800 . . . . . 6 (𝐴 = ∅ → 𝑥𝐵 𝐴 = 𝐴)
83, 7ja 189 . . . . 5 ((𝐵 = ∅ → 𝐴 = ∅) → 𝑥𝐵 𝐴 = 𝐴)
98eqcomd 2745 . . . 4 ((𝐵 = ∅ → 𝐴 = ∅) → 𝐴 = 𝑥𝐵 𝐴)
109uneq1d 4062 . . 3 ((𝐵 = ∅ → 𝐴 = ∅) → (𝐴 𝑥𝐵 𝑥) = ( 𝑥𝐵 𝐴 𝑥𝐵 𝑥))
11 uniiun 4954 . . . 4 𝐵 = 𝑥𝐵 𝑥
1211uneq2i 4060 . . 3 (𝐴 𝐵) = (𝐴 𝑥𝐵 𝑥)
13 iunun 4988 . . 3 𝑥𝐵 (𝐴𝑥) = ( 𝑥𝐵 𝐴 𝑥𝐵 𝑥)
1410, 12, 133eqtr4g 2799 . 2 ((𝐵 = ∅ → 𝐴 = ∅) → (𝐴 𝐵) = 𝑥𝐵 (𝐴𝑥))
15 unieq 4817 . . . . . . 7 (𝐵 = ∅ → 𝐵 = ∅)
16 uni0 4836 . . . . . . 7 ∅ = ∅
1715, 16eqtrdi 2790 . . . . . 6 (𝐵 = ∅ → 𝐵 = ∅)
1817uneq2d 4063 . . . . 5 (𝐵 = ∅ → (𝐴 𝐵) = (𝐴 ∪ ∅))
19 un0 4289 . . . . 5 (𝐴 ∪ ∅) = 𝐴
2018, 19eqtrdi 2790 . . . 4 (𝐵 = ∅ → (𝐴 𝐵) = 𝐴)
21 iuneq1 4907 . . . . 5 (𝐵 = ∅ → 𝑥𝐵 (𝐴𝑥) = 𝑥 ∈ ∅ (𝐴𝑥))
22 0iun 4958 . . . . 5 𝑥 ∈ ∅ (𝐴𝑥) = ∅
2321, 22eqtrdi 2790 . . . 4 (𝐵 = ∅ → 𝑥𝐵 (𝐴𝑥) = ∅)
2420, 23eqeq12d 2755 . . 3 (𝐵 = ∅ → ((𝐴 𝐵) = 𝑥𝐵 (𝐴𝑥) ↔ 𝐴 = ∅))
2524biimpcd 252 . 2 ((𝐴 𝐵) = 𝑥𝐵 (𝐴𝑥) → (𝐵 = ∅ → 𝐴 = ∅))
2614, 25impbii 212 1 ((𝐵 = ∅ → 𝐴 = ∅) ↔ (𝐴 𝐵) = 𝑥𝐵 (𝐴𝑥))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wb 209   = wceq 1542  wne 2935  cun 3851  c0 4221   cuni 4806   ciun 4891
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1802  ax-4 1816  ax-5 1917  ax-6 1975  ax-7 2020  ax-8 2116  ax-9 2124  ax-11 2162  ax-12 2179  ax-ext 2711
This theorem depends on definitions:  df-bi 210  df-an 400  df-or 847  df-tru 1545  df-fal 1555  df-ex 1787  df-nf 1791  df-sb 2075  df-clab 2718  df-cleq 2731  df-clel 2812  df-ne 2936  df-ral 3059  df-rex 3060  df-v 3402  df-dif 3856  df-un 3858  df-in 3860  df-ss 3870  df-nul 4222  df-sn 4527  df-uni 4807  df-iun 4893
This theorem is referenced by: (None)
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