intro (c//d)
ℕ : Type
inst✝¹ : Natural ℕ
ℤ : Type
inst✝ : Integer ℤ
a b : ℤ
denominator_positive✝ : AP (Positive b)
⊢ ∀ {q : Fraction ℤ}, sgn (a//b * q) ≃ sgn (a//b) * sgn q
ℕ : Type
inst✝¹ : Natural ℕ
ℤ : Type
inst✝ : Integer ℤ
a b : ℤ
denominator_positive✝¹ : AP (Positive b)
c d : ℤ
denominator_positive✝ : AP (Positive d)
⊢ sgn (a//b * c//d) ≃ sgn (a//b) * sgn (c//d)