have : n₁ ≃ n₂ := AA.inject ‹step n₁ ≃ step n₂›
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
n₁✝ n₂✝¹ m n₁ : ℕ
ih : ∀ (y : ℕ), n₁ ≃ y → n₁ * m ≃ y * m
n₂✝ n₂ : ℕ
x✝ : step n₁ ≃ step n₂
⊢ step n₁ * m ≃ step n₂ * m
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
n₁✝ n₂✝¹ m n₁ : ℕ
ih : ∀ (y : ℕ), n₁ ≃ y → n₁ * m ≃ y * m
n₂✝ n₂ : ℕ
x✝ : step n₁ ≃ step n₂
this : n₁ ≃ n₂
⊢ step n₁ * m ≃ step n₂ * m