English
For x,y ∈ α, dist (x : Completion α) y = dist x y. Thus the distance on the completion extends the original distance.
Русский
Для x,y ∈ α верно dist( x в Completion α, y ) = dist x y. Таким образом, расстояние на завершении extension оригинального расстояния.
LaTeX
$$$\operatorname{dist}(x:\mathrm{Completion}\;\alpha, y)=\operatorname{dist}(x,y)$$$
Lean4
/-- The new distance is an extension of the original distance. -/
@[simp]
protected theorem dist_eq (x y : α) : dist (x : Completion α) y = dist x y :=
Completion.extension₂_coe_coe uniformContinuous_dist _
_
/- Let us check that the new distance satisfies the axioms of a distance, by starting from the
properties on α and extending them to `Completion α` by continuity. -/