English
In any monoid R acting on M, the unit element 1 of R acts regularly on M; that is, 1 is M-regular.
Русский
В любом моноиде R, действующем на M, единица 1 действует регулярно на M; то есть 1-регулярен на M.
LaTeX
$$$\mathrm{IsSMulRegular}_M(1)\;\text{holds.}$$$
Lean4
/-- One is always `M`-regular. -/
@[simp]
theorem one : IsSMulRegular M (1 : R) := fun a b ab =>
by
dsimp only [Function.comp_def] at ab
rw [one_smul, one_smul] at ab
assumption