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Description: Greatest lower bounds in a topology are realized by the interior of the intersection. (Contributed by Zhi Wang, 30-Sep-2024)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | topclat.i | |- I = ( toInc ` J ) |
|
| toplatlub.j | |- ( ph -> J e. Top ) |
||
| toplatlub.s | |- ( ph -> S C_ J ) |
||
| toplatglb.g | |- G = ( glb ` I ) |
||
| toplatglb.e | |- ( ph -> S =/= (/) ) |
||
| Assertion | toplatglb | |- ( ph -> ( G ` S ) = ( ( int ` J ) ` |^| S ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | topclat.i | |- I = ( toInc ` J ) |
|
| 2 | toplatlub.j | |- ( ph -> J e. Top ) |
|
| 3 | toplatlub.s | |- ( ph -> S C_ J ) |
|
| 4 | toplatglb.g | |- G = ( glb ` I ) |
|
| 5 | toplatglb.e | |- ( ph -> S =/= (/) ) |
|
| 6 | 4 | a1i | |- ( ph -> G = ( glb ` I ) ) |
| 7 | intssuni | |- ( S =/= (/) -> |^| S C_ U. S ) |
|
| 8 | 5 7 | syl | |- ( ph -> |^| S C_ U. S ) |
| 9 | 3 | unissd | |- ( ph -> U. S C_ U. J ) |
| 10 | 8 9 | sstrd | |- ( ph -> |^| S C_ U. J ) |
| 11 | eqid | |- U. J = U. J |
|
| 12 | 11 | ntrval | |- ( ( J e. Top /\ |^| S C_ U. J ) -> ( ( int ` J ) ` |^| S ) = U. ( J i^i ~P |^| S ) ) |
| 13 | 2 10 12 | syl2anc | |- ( ph -> ( ( int ` J ) ` |^| S ) = U. ( J i^i ~P |^| S ) ) |
| 14 | 2 | uniexd | |- ( ph -> U. J e. _V ) |
| 15 | 14 10 | ssexd | |- ( ph -> |^| S e. _V ) |
| 16 | inpw | |- ( |^| S e. _V -> ( J i^i ~P |^| S ) = { x e. J | x C_ |^| S } ) |
|
| 17 | 16 | unieqd | |- ( |^| S e. _V -> U. ( J i^i ~P |^| S ) = U. { x e. J | x C_ |^| S } ) |
| 18 | 15 17 | syl | |- ( ph -> U. ( J i^i ~P |^| S ) = U. { x e. J | x C_ |^| S } ) |
| 19 | 13 18 | eqtrd | |- ( ph -> ( ( int ` J ) ` |^| S ) = U. { x e. J | x C_ |^| S } ) |
| 20 | 11 | ntropn | |- ( ( J e. Top /\ |^| S C_ U. J ) -> ( ( int ` J ) ` |^| S ) e. J ) |
| 21 | 2 10 20 | syl2anc | |- ( ph -> ( ( int ` J ) ` |^| S ) e. J ) |
| 22 | 1 2 3 6 19 21 | ipoglb | |- ( ph -> ( G ` S ) = ( ( int ` J ) ` |^| S ) ) |