English
If p is prime and p is associated with q, then q is prime.
Русский
Если p — простое и p ассоциировано с q, то q простое.
LaTeX
$$$ [CommMonoidWithZero M] {p q : M} (h : p ~ᵤ q) (hp : Prime p) : Prime q $$$
Lean4
protected theorem prime [CommMonoidWithZero M] {p q : M} (h : p ~ᵤ q) (hp : Prime p) : Prime q :=
⟨h.ne_zero_iff.1 hp.ne_zero,
let ⟨u, hu⟩ := h
⟨fun ⟨v, hv⟩ => hp.not_unit ⟨v * u⁻¹, by simp [hv, hu.symm]⟩,
hu ▸ by
simp only [Units.isUnit, IsUnit.mul_right_dvd]
intro a b
exact hp.dvd_or_dvd⟩⟩