English
The principal ideal generated by a equals the principal ideal generated by |a| in ℤ.
Русский
Идеал, порожденный a, совпадает с идеалом, порожденным |a|, в целых.
LaTeX
$$$\\operatorname{Ideal.span} \\{ |a| \\} = \\operatorname{Ideal.span} \\{ a \\}.$$$
Lean4
theorem span_natAbs (a : ℤ) : Ideal.span ({(a.natAbs : ℤ)} : Set ℤ) = Ideal.span { a } :=
by
rw [Ideal.span_singleton_eq_span_singleton]
exact (associated_natAbs _).symm