Variables (aT rT : finGroupType) (x : aT) (y : rT).
Definition eltm of #[y] %| #[x] := fun x_i => y ^+ invm (injm_Zpm x) x_i.
Hypothesis dvd_y_x : #[y] %| #[x].

Lemma cycle_subgroup_char a (H : {group gT}) : H \subset <[a]> -> H \char <[a]>.
End CycleSubGroup.