calc
p * q ≃ _ := mul_substR ‹q ≃ 0›
p * 0 ≃ _ := mul_absorbR
0     ≃ _ := eqv_refl
ℕ ℤ ℚ : Type
inst✝⁹ : Natural ℕ
inst✝⁸ : Integer ℤ
inst✝⁷ : Core ℚ
inst✝⁶ : Addition ℚ
inst✝⁵ : Multiplication ℚ
inst✝⁴ : Negation ℚ
inst✝³ : Subtraction ℚ
inst✝² : Reciprocation ℚ
inst✝¹ : Division ℚ
inst✝ : Sign ℚ
p q : ℚ
x✝ : p ≃ 0 ∨ q ≃ 0
h✝ : q ≃ 0
⊢ p * q ≃ 0
no goals