have : sgn b ≃ 1 := Integer.sgn_positive.mp this
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)
x✝ : a//b ≃ c//d
this✝ : a * d ≃ c * b
this : Positive b
⊢ sgn (a//b) ≃ sgn (c//d)
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)
x✝ : a//b ≃ c//d
this✝¹ : a * d ≃ c * b
this✝ : Positive b
this : sgn b ≃ 1
⊢ sgn (a//b) ≃ sgn (c//d)