English
The count of the unit ideal equals zero: count(K, v, 1) = 0.
Русский
Счёт единицы равен нулю: count(K, v, 1) = 0.
LaTeX
$$$$\\operatorname{count}(K,v,1)=0.$$$$
Lean4
/-- val_v(1) = 0. -/
theorem count_one : count K v (1 : FractionalIdeal R⁰ K) = 0 :=
by
have h1 : (1 : FractionalIdeal R⁰ K) = spanSingleton R⁰ ((algebraMap R K) 1)⁻¹ * ↑(1 : Ideal R) := by
rw [(algebraMap R K).map_one, Ideal.one_eq_top, coeIdeal_top, mul_one, inv_one, spanSingleton_one]
rw [count_well_defined K v one_ne_zero h1, Ideal.span_singleton_one, Ideal.one_eq_top, sub_self]