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Theorem uniopn 21505
 Description: The union of a subset of a topology (that is, the union of any family of open sets of a topology) is an open set. (Contributed by Stefan Allan, 27-Feb-2006.)
Assertion
Ref Expression
uniopn ((𝐽 ∈ Top ∧ 𝐴𝐽) → 𝐴𝐽)

Proof of Theorem uniopn
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 istopg 21503 . . . . 5 (𝐽 ∈ Top → (𝐽 ∈ Top ↔ (∀𝑥(𝑥𝐽 𝑥𝐽) ∧ ∀𝑥𝐽𝑦𝐽 (𝑥𝑦) ∈ 𝐽)))
21ibi 270 . . . 4 (𝐽 ∈ Top → (∀𝑥(𝑥𝐽 𝑥𝐽) ∧ ∀𝑥𝐽𝑦𝐽 (𝑥𝑦) ∈ 𝐽))
32simpld 498 . . 3 (𝐽 ∈ Top → ∀𝑥(𝑥𝐽 𝑥𝐽))
4 elpw2g 5233 . . . . . . . 8 (𝐽 ∈ Top → (𝐴 ∈ 𝒫 𝐽𝐴𝐽))
54biimpar 481 . . . . . . 7 ((𝐽 ∈ Top ∧ 𝐴𝐽) → 𝐴 ∈ 𝒫 𝐽)
6 sseq1 3978 . . . . . . . . 9 (𝑥 = 𝐴 → (𝑥𝐽𝐴𝐽))
7 unieq 4835 . . . . . . . . . 10 (𝑥 = 𝐴 𝑥 = 𝐴)
87eleq1d 2900 . . . . . . . . 9 (𝑥 = 𝐴 → ( 𝑥𝐽 𝐴𝐽))
96, 8imbi12d 348 . . . . . . . 8 (𝑥 = 𝐴 → ((𝑥𝐽 𝑥𝐽) ↔ (𝐴𝐽 𝐴𝐽)))
109spcgv 3581 . . . . . . 7 (𝐴 ∈ 𝒫 𝐽 → (∀𝑥(𝑥𝐽 𝑥𝐽) → (𝐴𝐽 𝐴𝐽)))
115, 10syl 17 . . . . . 6 ((𝐽 ∈ Top ∧ 𝐴𝐽) → (∀𝑥(𝑥𝐽 𝑥𝐽) → (𝐴𝐽 𝐴𝐽)))
1211com23 86 . . . . 5 ((𝐽 ∈ Top ∧ 𝐴𝐽) → (𝐴𝐽 → (∀𝑥(𝑥𝐽 𝑥𝐽) → 𝐴𝐽)))
1312ex 416 . . . 4 (𝐽 ∈ Top → (𝐴𝐽 → (𝐴𝐽 → (∀𝑥(𝑥𝐽 𝑥𝐽) → 𝐴𝐽))))
1413pm2.43d 53 . . 3 (𝐽 ∈ Top → (𝐴𝐽 → (∀𝑥(𝑥𝐽 𝑥𝐽) → 𝐴𝐽)))
153, 14mpid 44 . 2 (𝐽 ∈ Top → (𝐴𝐽 𝐴𝐽))
1615imp 410 1 ((𝐽 ∈ Top ∧ 𝐴𝐽) → 𝐴𝐽)
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ∧ wa 399  ∀wal 1536   = wceq 1538   ∈ wcel 2115  ∀wral 3133   ∩ cin 3918   ⊆ wss 3919  𝒫 cpw 4522  ∪ cuni 4824  Topctop 21501 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1912  ax-6 1971  ax-7 2016  ax-8 2117  ax-9 2125  ax-10 2146  ax-11 2162  ax-12 2179  ax-ext 2796  ax-sep 5189 This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845  df-tru 1541  df-ex 1782  df-nf 1786  df-sb 2071  df-clab 2803  df-cleq 2817  df-clel 2896  df-nfc 2964  df-ral 3138  df-rab 3142  df-v 3482  df-in 3926  df-ss 3936  df-pw 4524  df-uni 4825  df-top 21502 This theorem is referenced by:  iunopn  21506  unopn  21511  0opn  21512  topopn  21514  tgtop  21581  ntropn  21657  toponmre  21701  neips  21721  txcmplem1  22249  unimopn  23106  metrest  23134  cnopn  23395  locfinreflem  31164  cvmscld  32577  mblfinlem3  35041  mblfinlem4  35042  ismblfin  35043
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