Metamath Proof Explorer |
< Previous
Next >
Nearby theorems |
||
Mirrors > Home > MPE Home > Th. List > unopn | Structured version Visualization version GIF version |
Description: The union of two open sets is open. (Contributed by Jeff Madsen, 2-Sep-2009.) |
Ref | Expression |
---|---|
unopn | ⊢ ((𝐽 ∈ Top ∧ 𝐴 ∈ 𝐽 ∧ 𝐵 ∈ 𝐽) → (𝐴 ∪ 𝐵) ∈ 𝐽) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | uniprg 4450 | . . 3 ⊢ ((𝐴 ∈ 𝐽 ∧ 𝐵 ∈ 𝐽) → ∪ {𝐴, 𝐵} = (𝐴 ∪ 𝐵)) | |
2 | 1 | 3adant1 1079 | . 2 ⊢ ((𝐽 ∈ Top ∧ 𝐴 ∈ 𝐽 ∧ 𝐵 ∈ 𝐽) → ∪ {𝐴, 𝐵} = (𝐴 ∪ 𝐵)) |
3 | prssi 4353 | . . . 4 ⊢ ((𝐴 ∈ 𝐽 ∧ 𝐵 ∈ 𝐽) → {𝐴, 𝐵} ⊆ 𝐽) | |
4 | uniopn 20702 | . . . 4 ⊢ ((𝐽 ∈ Top ∧ {𝐴, 𝐵} ⊆ 𝐽) → ∪ {𝐴, 𝐵} ∈ 𝐽) | |
5 | 3, 4 | sylan2 491 | . . 3 ⊢ ((𝐽 ∈ Top ∧ (𝐴 ∈ 𝐽 ∧ 𝐵 ∈ 𝐽)) → ∪ {𝐴, 𝐵} ∈ 𝐽) |
6 | 5 | 3impb 1260 | . 2 ⊢ ((𝐽 ∈ Top ∧ 𝐴 ∈ 𝐽 ∧ 𝐵 ∈ 𝐽) → ∪ {𝐴, 𝐵} ∈ 𝐽) |
7 | 2, 6 | eqeltrrd 2702 | 1 ⊢ ((𝐽 ∈ Top ∧ 𝐴 ∈ 𝐽 ∧ 𝐵 ∈ 𝐽) → (𝐴 ∪ 𝐵) ∈ 𝐽) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 384 ∧ w3a 1037 = wceq 1483 ∈ wcel 1990 ∪ cun 3572 ⊆ wss 3574 {cpr 4179 ∪ 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-3an 1039 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-un 3579 df-in 3581 df-ss 3588 df-pw 4160 df-sn 4178 df-pr 4180 df-uni 4437 df-top 20699 |
This theorem is referenced by: comppfsc 21335 txcld 21406 icccld 22570 icccncfext 40100 |
Copyright terms: Public domain | W3C validator |