case mp =>
  intro (_ : p ≃ q)
  show sgn (p - q) ≃ 0
  have : p - q ≃ 0 := sub_eqv_zero_iff_eqv.mpr ‹p ≃ q›
  have : sgn (p - q) ≃ 0 := sgn_zero.mp this
  exact this
ℕ ℤ ℚ : Type
inst✝¹⁰ : Natural ℕ
inst✝⁹ : Integer ℤ
inst✝⁸ : Core ℚ
inst✝⁷ : Addition ℚ
inst✝⁶ : Multiplication ℚ
inst✝⁵ : Negation ℚ
inst✝⁴ : Sign ℚ
inst✝³ : Subtraction ℚ
inst✝² : Reciprocation ℚ
inst✝¹ : Division ℚ
inst✝ : Order ℚ
p q : ℚ
⊢ p ≃ q → sgn (p - q) ≃ 0
no goals