have : Positive (n * m) :=
  positive_subst (Rel.symm ‹n * m ≃ 1›) one_positive
ℕ : Type
inst✝⁵ : Core ℕ
inst✝⁴ : Induction ℕ
inst✝³ : Addition ℕ
inst✝² : Sign ℕ
inst✝¹ : Order ℕ
inst✝ : Multiplication ℕ
n m : ℕ
x✝ : n * m ≃ 1
⊢ n ≃ 1 ∧ m ≃ 1
ℕ : Type
inst✝⁵ : Core ℕ
inst✝⁴ : Induction ℕ
inst✝³ : Addition ℕ
inst✝² : Sign ℕ
inst✝¹ : Order ℕ
inst✝ : Multiplication ℕ
n m : ℕ
x✝ : n * m ≃ 1
this : Positive (n * m)
⊢ n ≃ 1 ∧ m ≃ 1