English
In a NormalizedGCDMonoid, lcm(a,b) = lcm(b,a).
Русский
В нормализованном gcd-монойде НОК симметрична: lcm(a,b) = lcm(b,a).
LaTeX
$$$ \operatorname{lcm}(a,b) = \operatorname{lcm}(b,a) $$$
Lean4
theorem lcm_comm [NormalizedGCDMonoid α] (a b : α) : lcm a b = lcm b a :=
dvd_antisymm_of_normalize_eq (normalize_lcm _ _) (normalize_lcm _ _) (lcm_dvd (dvd_lcm_right _ _) (dvd_lcm_left _ _))
(lcm_dvd (dvd_lcm_right _ _) (dvd_lcm_left _ _))