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Mirrors > Home > MPE Home > Th. List > en1top | Structured version Visualization version GIF version |
Description: {∅} is the only topology with one element. (Contributed by FL, 18-Aug-2008.) |
Ref | Expression |
---|---|
en1top | ⊢ (𝐽 ∈ Top → (𝐽 ≈ 1o ↔ 𝐽 = {∅})) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0opn 22757 | . . 3 ⊢ (𝐽 ∈ Top → ∅ ∈ 𝐽) | |
2 | en1eqsn 9273 | . . . 4 ⊢ ((∅ ∈ 𝐽 ∧ 𝐽 ≈ 1o) → 𝐽 = {∅}) | |
3 | 2 | ex 412 | . . 3 ⊢ (∅ ∈ 𝐽 → (𝐽 ≈ 1o → 𝐽 = {∅})) |
4 | 1, 3 | syl 17 | . 2 ⊢ (𝐽 ∈ Top → (𝐽 ≈ 1o → 𝐽 = {∅})) |
5 | id 22 | . . 3 ⊢ (𝐽 = {∅} → 𝐽 = {∅}) | |
6 | 0ex 5300 | . . . 4 ⊢ ∅ ∈ V | |
7 | 6 | ensn1 9016 | . . 3 ⊢ {∅} ≈ 1o |
8 | 5, 7 | eqbrtrdi 5180 | . 2 ⊢ (𝐽 = {∅} → 𝐽 ≈ 1o) |
9 | 4, 8 | impbid1 224 | 1 ⊢ (𝐽 ∈ Top → (𝐽 ≈ 1o ↔ 𝐽 = {∅})) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 205 = wceq 1533 ∈ wcel 2098 ∅c0 4317 {csn 4623 class class class wbr 5141 1oc1o 8457 ≈ cen 8935 Topctop 22746 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1789 ax-4 1803 ax-5 1905 ax-6 1963 ax-7 2003 ax-8 2100 ax-9 2108 ax-10 2129 ax-11 2146 ax-12 2163 ax-ext 2697 ax-sep 5292 ax-nul 5299 ax-pr 5420 |
This theorem depends on definitions: df-bi 206 df-an 396 df-or 845 df-3an 1086 df-tru 1536 df-fal 1546 df-ex 1774 df-nf 1778 df-sb 2060 df-mo 2528 df-eu 2557 df-clab 2704 df-cleq 2718 df-clel 2804 df-ne 2935 df-ral 3056 df-rex 3065 df-reu 3371 df-rab 3427 df-v 3470 df-dif 3946 df-un 3948 df-in 3950 df-ss 3960 df-nul 4318 df-if 4524 df-pw 4599 df-sn 4624 df-pr 4626 df-op 4630 df-uni 4903 df-br 5142 df-opab 5204 df-id 5567 df-xp 5675 df-rel 5676 df-cnv 5677 df-co 5678 df-dm 5679 df-rn 5680 df-res 5681 df-ima 5682 df-suc 6363 df-iota 6488 df-fun 6538 df-fn 6539 df-f 6540 df-f1 6541 df-fo 6542 df-f1o 6543 df-fv 6544 df-1o 8464 df-en 8939 df-top 22747 |
This theorem is referenced by: hmph0 23650 |
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