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lowasser committed Feb 14, 2025
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14 changes: 7 additions & 7 deletions src/real-numbers/arithmetically-located-dedekind-cuts.lagda.md
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Expand Up @@ -42,18 +42,19 @@ open import real-numbers.upper-dedekind-real-numbers

## Definition

A pair of a [lower Dedekind real](real-numbers.lower-dedekind-real-numbers.md)
`L` and an [upper Dedekind real](real-numbers.upper-dedekind-real-numbers.md)
A pair of a [lower Dedekind cut](real-numbers.lower-dedekind-real-numbers.md)
`L` and an [upper Dedekind cut](real-numbers.upper-dedekind-real-numbers.md)
`U` is {{#concept "arithmetically located" Disambiguation="Dedekind cut" Agda=arithmetically-located-lower-upper-ℝ}} if
for any positive [rational number](elementary-number-theory.rational-numbers.md)
`ε : ℚ`, there exists `p, q : ℚ` where `p ∈ L` and `q ∈ U`, such that
for any [positive](elementary-number-theory.positive-rational-numbers.md)
[rational number](elementary-number-theory.rational-numbers.md)
`ε : ℚ⁺`, there exists `p, q : ℚ` where `p ∈ L` and `q ∈ U`, such that
`0 < q - p < ε`. Intuitively, when `L , U` represent the cuts of a real number
`x`, `p` and `q` are rational approximations of `x` to within `ε`. This follows
parts of Section 11 in {{#cite BauerTaylor2009}}.

## Definitions

### The predicate of being arithmetically located on pairs of subtypes of rational numbers
### The predicate of being arithmetically located on pairs of lower and upper Dedekind real numbers

```agda
module _
Expand All @@ -74,8 +75,7 @@ module _

### Arithmetically located cuts are located

If a cut is arithmetically located and closed under strict inequality on the
rational numbers, it is also located.
If a pair of lower and upper Dedekind cuts is arithmetically located, it is also located.

```agda
module _
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