English
For any natural n and unit x of R, the valuation of its image in K modulo n equals 1 in the Selmer context.
Русский
Для любого n и единицы x в R, оценка образа в K по модулю n равна 1 в контексте Selmer.
LaTeX
$$valuation_of_unit_mod_eq (n) (x) : S(valuation)(image_of_x) = 1$$
Lean4
@[simp]
theorem valuation_of_unit_mod_eq (n : ℕ) (x : Rˣ) :
v.valuationOfNeZeroMod n (Units.map (algebraMap R K : R →* K) x : K / n) = 1 := by
-- This used to be `rw`, but we need `erw` after https://github.com/leanprover/lean4/pull/2644
erw [valuationOfNeZeroMod, MonoidHom.comp_apply, ← QuotientGroup.coe_mk',
QuotientGroup.map_mk' (G := Kˣ) (N := MonoidHom.range (powMonoidHom n)), valuation_of_unit_eq, QuotientGroup.mk_one,
map_one]