convert sub_dvd_eval_sub ((fun x => P.eval x)^[n + 1] t) ((fun x => P.eval x)^[n] t) P <;>
  rw [Function.iterate_succ_apply']
P : ℤ[X]
t : ℤ
ht : t ∈ periodicPts fun x => Polynomial.eval x P
C : Cycle ℤ := Cycle.map (fun x => Polynomial.eval x P - x) (periodicOrbit (fun x => Polynomial.eval x P) t)
HC : ∀ {n : ℕ}, (fun x => Polynomial.eval x P)^[n + 1] t - (fun x => Polynomial.eval x P)^[n] t ∈ C
n : ℕ
⊢ Polynomial.eval ((fun x => Polynomial.eval x P)^[n] t) P - (fun x => Polynomial.eval x P)^[n] t ∣
    Polynomial.eval ((fun x => Polynomial.eval x P)^[n + 1] t) P - (fun x => Polynomial.eval x P)^[n + 1] t
no goals