English
If R is a monoid, an element in Rˣ is regular.
Русский
Если R — моноид, элемент в Rˣ регулярен.
LaTeX
$$$ IsRegular (a : R) \text{ for } a \in Rˣ $$$
Lean4
/-- If `R` is a monoid, an element in `Rˣ` is regular. -/
@[to_additive /-- If `R` is an additive monoid, an element in `add_units R` is add-regular. -/
]
theorem isRegular (a : Rˣ) : IsRegular (a : R) :=
⟨isLeftRegular_of_mul_eq_one a.inv_mul, isRightRegular_of_mul_eq_one a.mul_inv⟩