English
If h is a primitive root ζ k and p ≠ 0 divides k, then ζ^p is a primitive root of order k/p.
Русский
Если h — примитивный корень ζ порядка k и p ≠ 0 делит k, то ζ^p — примитивный корень порядка k/p.
LaTeX
$$$$\text{If } h: IsPrimitiveRoot(\zeta,k) \text{ and } p \ne 0 \text{ and } p \mid k, \text{ then } IsPrimitiveRoot(\zeta^p, k/p).$$$$
Lean4
theorem pow_of_dvd (h : IsPrimitiveRoot ζ k) {p : ℕ} (hp : p ≠ 0) (hdiv : p ∣ k) : IsPrimitiveRoot (ζ ^ p) (k / p) :=
by
rw [h.eq_orderOf] at hdiv ⊢
rw [← orderOf_pow_of_dvd hp hdiv]
exact IsPrimitiveRoot.orderOf _