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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 a topology. (Contributed by Stefan Allan, 27-Feb-2006.) |
Ref | Expression |
---|---|
0opn | ⊢ (𝐽 ∈ Top → ∅ ∈ 𝐽) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | uni0 4465 | . 2 ⊢ ∪ ∅ = ∅ | |
2 | 0ss 3972 | . . 3 ⊢ ∅ ⊆ 𝐽 | |
3 | uniopn 20702 | . . 3 ⊢ ((𝐽 ∈ Top ∧ ∅ ⊆ 𝐽) → ∪ ∅ ∈ 𝐽) | |
4 | 2, 3 | mpan2 707 | . 2 ⊢ (𝐽 ∈ Top → ∪ ∅ ∈ 𝐽) |
5 | 1, 4 | syl5eqelr 2706 | 1 ⊢ (𝐽 ∈ Top → ∅ ∈ 𝐽) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∈ wcel 1990 ⊆ wss 3574 ∅c0 3915 ∪ cuni 4436 Topctop 20698 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1722 ax-4 1737 ax-5 1839 ax-6 1888 ax-7 1935 ax-9 1999 ax-10 2019 ax-11 2034 ax-12 2047 ax-13 2246 ax-ext 2602 ax-sep 4781 |
This theorem depends on definitions: df-bi 197 df-or 385 df-an 386 df-tru 1486 df-ex 1705 df-nf 1710 df-sb 1881 df-clab 2609 df-cleq 2615 df-clel 2618 df-nfc 2753 df-ral 2917 df-rex 2918 df-v 3202 df-dif 3577 df-in 3581 df-ss 3588 df-nul 3916 df-pw 4160 df-sn 4178 df-uni 4437 df-top 20699 |
This theorem is referenced by: 0ntop 20710 topgele 20734 tgclb 20774 0top 20787 en1top 20788 en2top 20789 topcld 20839 clsval2 20854 ntr0 20885 opnnei 20924 0nei 20932 restrcl 20961 rest0 20973 ordtrest2lem 21007 iocpnfordt 21019 icomnfordt 21020 cnindis 21096 isconn2 21217 kqtop 21548 mopn0 22303 locfinref 29908 ordtrest2NEWlem 29968 sxbrsigalem3 30334 cnambfre 33458 |
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