English
In a densely ordered set, no pair a,b is in CovBy relation.
Русский
Во плотно упорядоченном множестве никакие две точки не образуют отношение CovBy.
LaTeX
$$$$\text{DenselyOrdered }\alpha\Rightarrow \neg(a\lessdot b).$$$$
Lean4
/-- In a dense order, nothing covers anything. -/
theorem not_covBy [DenselyOrdered α] : ¬a ⋖ b := fun h =>
let ⟨_, hc⟩ := exists_between h.1
h.2 hc.1 hc.2