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Theorem ldlfcntref 32492
Description: Every open cover of a LindelΓΆf space has a countable refinement. (Contributed by Thierry Arnoux, 1-Feb-2020.)
Hypothesis
Ref Expression
ldlfcntref.x 𝑋 = βˆͺ 𝐽
Assertion
Ref Expression
ldlfcntref ((𝐽 ∈ Ldlf ∧ π‘ˆ βŠ† 𝐽 ∧ 𝑋 = βˆͺ π‘ˆ) β†’ βˆƒπ‘£ ∈ 𝒫 𝐽(𝑣 β‰Ό Ο‰ ∧ 𝑣Refπ‘ˆ))
Distinct variable groups:   𝑣,𝐽   𝑣,π‘ˆ
Allowed substitution hint:   𝑋(𝑣)

Proof of Theorem ldlfcntref
Dummy variable π‘₯ is distinct from all other variables.
StepHypRef Expression
1 ldlfcntref.x . 2 𝑋 = βˆͺ 𝐽
2 df-ldlf 32491 . 2 Ldlf = CovHasRef{π‘₯ ∣ π‘₯ β‰Ό Ο‰}
3 vex 3448 . . . 4 𝑣 ∈ V
4 breq1 5109 . . . 4 (π‘₯ = 𝑣 β†’ (π‘₯ β‰Ό Ο‰ ↔ 𝑣 β‰Ό Ο‰))
53, 4elab 3631 . . 3 (𝑣 ∈ {π‘₯ ∣ π‘₯ β‰Ό Ο‰} ↔ 𝑣 β‰Ό Ο‰)
65biimpi 215 . 2 (𝑣 ∈ {π‘₯ ∣ π‘₯ β‰Ό Ο‰} β†’ 𝑣 β‰Ό Ο‰)
71, 2, 6crefdf 32486 1 ((𝐽 ∈ Ldlf ∧ π‘ˆ βŠ† 𝐽 ∧ 𝑋 = βˆͺ π‘ˆ) β†’ βˆƒπ‘£ ∈ 𝒫 𝐽(𝑣 β‰Ό Ο‰ ∧ 𝑣Refπ‘ˆ))
Colors of variables: wff setvar class
Syntax hints:   β†’ wi 4   ∧ wa 397   ∧ w3a 1088   = wceq 1542   ∈ wcel 2107  {cab 2710  βˆƒwrex 3070   βŠ† wss 3911  π’« cpw 4561  βˆͺ cuni 4866   class class class wbr 5106  Ο‰com 7803   β‰Ό cdom 8884  Refcref 22869  Ldlfcldlf 32490
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1914  ax-6 1972  ax-7 2012  ax-8 2109  ax-9 2117  ax-ext 2704  ax-sep 5257
This theorem depends on definitions:  df-bi 206  df-an 398  df-or 847  df-3an 1090  df-tru 1545  df-fal 1555  df-ex 1783  df-sb 2069  df-clab 2711  df-cleq 2725  df-clel 2811  df-ral 3062  df-rex 3071  df-rab 3407  df-v 3446  df-dif 3914  df-un 3916  df-in 3918  df-ss 3928  df-nul 4284  df-if 4488  df-pw 4563  df-sn 4588  df-pr 4590  df-op 4594  df-uni 4867  df-br 5107  df-cref 32481  df-ldlf 32491
This theorem is referenced by: (None)
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