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Theorem ist1-2 23355
Description: An alternate characterization of T1 spaces. (Contributed by Jeff Hankins, 31-Jan-2010.) (Proof shortened by Mario Carneiro, 24-Aug-2015.)
Assertion
Ref Expression
ist1-2 (𝐽 ∈ (TopOn‘𝑋) → (𝐽 ∈ Fre ↔ ∀𝑥𝑋𝑦𝑋 (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦)))
Distinct variable groups:   𝑥,𝑦,𝑜,𝐽   𝑜,𝑋,𝑥,𝑦

Proof of Theorem ist1-2
StepHypRef Expression
1 topontop 22919 . . 3 (𝐽 ∈ (TopOn‘𝑋) → 𝐽 ∈ Top)
2 eqid 2737 . . . . 5 𝐽 = 𝐽
32ist1 23329 . . . 4 (𝐽 ∈ Fre ↔ (𝐽 ∈ Top ∧ ∀𝑦 𝐽{𝑦} ∈ (Clsd‘𝐽)))
43baib 535 . . 3 (𝐽 ∈ Top → (𝐽 ∈ Fre ↔ ∀𝑦 𝐽{𝑦} ∈ (Clsd‘𝐽)))
51, 4syl 17 . 2 (𝐽 ∈ (TopOn‘𝑋) → (𝐽 ∈ Fre ↔ ∀𝑦 𝐽{𝑦} ∈ (Clsd‘𝐽)))
6 toponuni 22920 . . 3 (𝐽 ∈ (TopOn‘𝑋) → 𝑋 = 𝐽)
76raleqdv 3326 . 2 (𝐽 ∈ (TopOn‘𝑋) → (∀𝑦𝑋 {𝑦} ∈ (Clsd‘𝐽) ↔ ∀𝑦 𝐽{𝑦} ∈ (Clsd‘𝐽)))
81adantr 480 . . . . . 6 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → 𝐽 ∈ Top)
9 eltop2 22982 . . . . . 6 (𝐽 ∈ Top → (( 𝐽 ∖ {𝑦}) ∈ 𝐽 ↔ ∀𝑥 ∈ ( 𝐽 ∖ {𝑦})∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))))
108, 9syl 17 . . . . 5 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → (( 𝐽 ∖ {𝑦}) ∈ 𝐽 ↔ ∀𝑥 ∈ ( 𝐽 ∖ {𝑦})∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))))
116eleq2d 2827 . . . . . . . 8 (𝐽 ∈ (TopOn‘𝑋) → (𝑦𝑋𝑦 𝐽))
1211biimpa 476 . . . . . . 7 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → 𝑦 𝐽)
1312snssd 4809 . . . . . 6 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → {𝑦} ⊆ 𝐽)
142iscld2 23036 . . . . . 6 ((𝐽 ∈ Top ∧ {𝑦} ⊆ 𝐽) → ({𝑦} ∈ (Clsd‘𝐽) ↔ ( 𝐽 ∖ {𝑦}) ∈ 𝐽))
158, 13, 14syl2anc 584 . . . . 5 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → ({𝑦} ∈ (Clsd‘𝐽) ↔ ( 𝐽 ∖ {𝑦}) ∈ 𝐽))
166adantr 480 . . . . . . . . 9 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → 𝑋 = 𝐽)
1716eleq2d 2827 . . . . . . . 8 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → (𝑥𝑋𝑥 𝐽))
1817imbi1d 341 . . . . . . 7 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → ((𝑥𝑋 → (𝑥𝑦 → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})))) ↔ (𝑥 𝐽 → (𝑥𝑦 → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))))))
19 con1b 358 . . . . . . . . 9 ((¬ 𝑥 = 𝑦 → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))) ↔ (¬ ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})) → 𝑥 = 𝑦))
20 df-ne 2941 . . . . . . . . . 10 (𝑥𝑦 ↔ ¬ 𝑥 = 𝑦)
2120imbi1i 349 . . . . . . . . 9 ((𝑥𝑦 → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))) ↔ (¬ 𝑥 = 𝑦 → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))))
22 disjsn 4711 . . . . . . . . . . . . . . 15 ((𝑜 ∩ {𝑦}) = ∅ ↔ ¬ 𝑦𝑜)
23 elssuni 4937 . . . . . . . . . . . . . . . 16 (𝑜𝐽𝑜 𝐽)
24 reldisj 4453 . . . . . . . . . . . . . . . 16 (𝑜 𝐽 → ((𝑜 ∩ {𝑦}) = ∅ ↔ 𝑜 ⊆ ( 𝐽 ∖ {𝑦})))
2523, 24syl 17 . . . . . . . . . . . . . . 15 (𝑜𝐽 → ((𝑜 ∩ {𝑦}) = ∅ ↔ 𝑜 ⊆ ( 𝐽 ∖ {𝑦})))
2622, 25bitr3id 285 . . . . . . . . . . . . . 14 (𝑜𝐽 → (¬ 𝑦𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})))
2726anbi2d 630 . . . . . . . . . . . . 13 (𝑜𝐽 → ((𝑥𝑜 ∧ ¬ 𝑦𝑜) ↔ (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))))
2827rexbiia 3092 . . . . . . . . . . . 12 (∃𝑜𝐽 (𝑥𝑜 ∧ ¬ 𝑦𝑜) ↔ ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})))
29 rexanali 3102 . . . . . . . . . . . 12 (∃𝑜𝐽 (𝑥𝑜 ∧ ¬ 𝑦𝑜) ↔ ¬ ∀𝑜𝐽 (𝑥𝑜𝑦𝑜))
3028, 29bitr3i 277 . . . . . . . . . . 11 (∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})) ↔ ¬ ∀𝑜𝐽 (𝑥𝑜𝑦𝑜))
3130con2bii 357 . . . . . . . . . 10 (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) ↔ ¬ ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})))
3231imbi1i 349 . . . . . . . . 9 ((∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦) ↔ (¬ ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})) → 𝑥 = 𝑦))
3319, 21, 323bitr4ri 304 . . . . . . . 8 ((∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦) ↔ (𝑥𝑦 → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))))
3433imbi2i 336 . . . . . . 7 ((𝑥𝑋 → (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦)) ↔ (𝑥𝑋 → (𝑥𝑦 → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})))))
35 eldifsn 4786 . . . . . . . . 9 (𝑥 ∈ ( 𝐽 ∖ {𝑦}) ↔ (𝑥 𝐽𝑥𝑦))
3635imbi1i 349 . . . . . . . 8 ((𝑥 ∈ ( 𝐽 ∖ {𝑦}) → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))) ↔ ((𝑥 𝐽𝑥𝑦) → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))))
37 impexp 450 . . . . . . . 8 (((𝑥 𝐽𝑥𝑦) → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))) ↔ (𝑥 𝐽 → (𝑥𝑦 → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})))))
3836, 37bitri 275 . . . . . . 7 ((𝑥 ∈ ( 𝐽 ∖ {𝑦}) → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))) ↔ (𝑥 𝐽 → (𝑥𝑦 → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})))))
3918, 34, 383bitr4g 314 . . . . . 6 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → ((𝑥𝑋 → (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦)) ↔ (𝑥 ∈ ( 𝐽 ∖ {𝑦}) → ∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦})))))
4039ralbidv2 3174 . . . . 5 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → (∀𝑥𝑋 (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦) ↔ ∀𝑥 ∈ ( 𝐽 ∖ {𝑦})∃𝑜𝐽 (𝑥𝑜𝑜 ⊆ ( 𝐽 ∖ {𝑦}))))
4110, 15, 403bitr4d 311 . . . 4 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝑦𝑋) → ({𝑦} ∈ (Clsd‘𝐽) ↔ ∀𝑥𝑋 (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦)))
4241ralbidva 3176 . . 3 (𝐽 ∈ (TopOn‘𝑋) → (∀𝑦𝑋 {𝑦} ∈ (Clsd‘𝐽) ↔ ∀𝑦𝑋𝑥𝑋 (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦)))
43 ralcom 3289 . . 3 (∀𝑦𝑋𝑥𝑋 (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦) ↔ ∀𝑥𝑋𝑦𝑋 (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦))
4442, 43bitrdi 287 . 2 (𝐽 ∈ (TopOn‘𝑋) → (∀𝑦𝑋 {𝑦} ∈ (Clsd‘𝐽) ↔ ∀𝑥𝑋𝑦𝑋 (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦)))
455, 7, 443bitr2d 307 1 (𝐽 ∈ (TopOn‘𝑋) → (𝐽 ∈ Fre ↔ ∀𝑥𝑋𝑦𝑋 (∀𝑜𝐽 (𝑥𝑜𝑦𝑜) → 𝑥 = 𝑦)))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wb 206  wa 395   = wceq 1540  wcel 2108  wne 2940  wral 3061  wrex 3070  cdif 3948  cin 3950  wss 3951  c0 4333  {csn 4626   cuni 4907  cfv 6561  Topctop 22899  TopOnctopon 22916  Clsdccld 23024  Frect1 23315
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-8 2110  ax-9 2118  ax-10 2141  ax-11 2157  ax-12 2177  ax-ext 2708  ax-sep 5296  ax-nul 5306  ax-pow 5365  ax-pr 5432  ax-un 7755
This theorem depends on definitions:  df-bi 207  df-an 396  df-or 849  df-3an 1089  df-tru 1543  df-fal 1553  df-ex 1780  df-nf 1784  df-sb 2065  df-mo 2540  df-eu 2569  df-clab 2715  df-cleq 2729  df-clel 2816  df-nfc 2892  df-ne 2941  df-ral 3062  df-rex 3071  df-rab 3437  df-v 3482  df-dif 3954  df-un 3956  df-in 3958  df-ss 3968  df-nul 4334  df-if 4526  df-pw 4602  df-sn 4627  df-pr 4629  df-op 4633  df-uni 4908  df-br 5144  df-opab 5206  df-mpt 5226  df-id 5578  df-xp 5691  df-rel 5692  df-cnv 5693  df-co 5694  df-dm 5695  df-iota 6514  df-fun 6563  df-fv 6569  df-topgen 17488  df-top 22900  df-topon 22917  df-cld 23027  df-t1 23322
This theorem is referenced by:  t1t0  23356  ist1-3  23357  haust1  23360  t1sep2  23377  isr0  23745  tgpt0  24127
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