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Mirrors > Home > MPE Home > Th. List > 0opn | Structured version Visualization version GIF version |
Description: The empty set is an open subset of any topology. (Contributed by Stefan Allan, 27-Feb-2006.) |
Ref | Expression |
---|---|
0opn | ⊢ (𝐽 ∈ Top → ∅ ∈ 𝐽) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | uni0 4828 | . 2 ⊢ ∪ ∅ = ∅ | |
2 | 0ss 4304 | . . 3 ⊢ ∅ ⊆ 𝐽 | |
3 | uniopn 21502 | . . 3 ⊢ ((𝐽 ∈ Top ∧ ∅ ⊆ 𝐽) → ∪ ∅ ∈ 𝐽) | |
4 | 2, 3 | mpan2 690 | . 2 ⊢ (𝐽 ∈ Top → ∪ ∅ ∈ 𝐽) |
5 | 1, 4 | eqeltrrid 2895 | 1 ⊢ (𝐽 ∈ Top → ∅ ∈ 𝐽) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∈ wcel 2111 ⊆ wss 3881 ∅c0 4243 ∪ cuni 4800 Topctop 21498 |
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 1911 ax-6 1970 ax-7 2015 ax-8 2113 ax-9 2121 ax-10 2142 ax-11 2158 ax-12 2175 ax-ext 2770 ax-sep 5167 |
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 2070 df-clab 2777 df-cleq 2791 df-clel 2870 df-nfc 2938 df-ral 3111 df-rex 3112 df-rab 3115 df-v 3443 df-dif 3884 df-in 3888 df-ss 3898 df-nul 4244 df-pw 4499 df-sn 4526 df-uni 4801 df-top 21499 |
This theorem is referenced by: 0ntop 21510 topgele 21535 tgclb 21575 0top 21588 en1top 21589 en2top 21590 topcld 21640 clsval2 21655 ntr0 21686 opnnei 21725 0nei 21733 restrcl 21762 rest0 21774 ordtrest2lem 21808 iocpnfordt 21820 icomnfordt 21821 cnindis 21897 isconn2 22019 kqtop 22350 mopn0 23105 locfinref 31194 ordtrest2NEWlem 31275 sxbrsigalem3 31640 cnambfre 35105 |
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