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Description: In an ordered field, the ring unity is strictly positive. (Contributed by Thierry Arnoux, 21-Jan-2018)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | orng0le1.1 | |- .0. = ( 0g ` F ) |
|
| orng0le1.2 | |- .1. = ( 1r ` F ) |
||
| ofld0lt1.3 | |- .< = ( lt ` F ) |
||
| Assertion | ofldlt1 | |- ( F e. oField -> .0. .< .1. ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | orng0le1.1 | |- .0. = ( 0g ` F ) |
|
| 2 | orng0le1.2 | |- .1. = ( 1r ` F ) |
|
| 3 | ofld0lt1.3 | |- .< = ( lt ` F ) |
|
| 4 | isofld | |- ( F e. oField <-> ( F e. Field /\ F e. oRing ) ) |
|
| 5 | 4 | simprbi | |- ( F e. oField -> F e. oRing ) |
| 6 | eqid | |- ( le ` F ) = ( le ` F ) |
|
| 7 | 1 2 6 | orng0le1 | |- ( F e. oRing -> .0. ( le ` F ) .1. ) |
| 8 | 5 7 | syl | |- ( F e. oField -> .0. ( le ` F ) .1. ) |
| 9 | ofldfld | |- ( F e. oField -> F e. Field ) |
|
| 10 | isfld | |- ( F e. Field <-> ( F e. DivRing /\ F e. CRing ) ) |
|
| 11 | 10 | simplbi | |- ( F e. Field -> F e. DivRing ) |
| 12 | 1 2 | drngunz | |- ( F e. DivRing -> .1. =/= .0. ) |
| 13 | 9 11 12 | 3syl | |- ( F e. oField -> .1. =/= .0. ) |
| 14 | 13 | necomd | |- ( F e. oField -> .0. =/= .1. ) |
| 15 | 1 | fvexi | |- .0. e. _V |
| 16 | 2 | fvexi | |- .1. e. _V |
| 17 | 6 3 | pltval | |- ( ( F e. oField /\ .0. e. _V /\ .1. e. _V ) -> ( .0. .< .1. <-> ( .0. ( le ` F ) .1. /\ .0. =/= .1. ) ) ) |
| 18 | 15 16 17 | mp3an23 | |- ( F e. oField -> ( .0. .< .1. <-> ( .0. ( le ` F ) .1. /\ .0. =/= .1. ) ) ) |
| 19 | 8 14 18 | mpbir2and | |- ( F e. oField -> .0. .< .1. ) |