∀ {O : Type u_1} [inst : CommRing O] {p : ℕ} [inst_1 : Fact (Nat.Prime p)] [inst_2 : Fact ¬IsUnit ↑p]
  [inst_3 : IsAdicComplete (Ideal.span {↑p}) O] (x x_1 : PreTilt O p), (x * x_1).untiltFun = x.untiltFun * x_1.untiltFun