English
Including the identity element 1 in the generating set does not change the generated submonoid: closure(insert(1) s) = closure(s).
Русский
Добавление единицы 1 к порождающему множеству не меняет порожденный подмоном: closure(insert(1) s) = closure(s).
LaTeX
$$$\\operatorname{closure}(\\mathrm{insert}(1, s)) = \\operatorname{closure}(s)$$$
Lean4
@[to_additive (attr := simp)]
theorem closure_insert_one (s : Set M) : closure (insert 1 s) = closure s :=
by
rw [insert_eq, closure_union, sup_eq_right, closure_singleton_le_iff_mem]
apply one_mem