fact: Definition mulℝ (x y : Re) : Re := fun ε q => Ex₄ ε₁,ε₂,q₁,q₂ ∈ ℚ+*×ℚ+*×ℚ×ℚ, {(|q₁| + (ε₁ + ε₁)) * (ε₂ + ε₂) + (|q₂| + (ε₂ + ε₂)) * (ε₁ + ε₁) <= ε & q = q₁ * q₂ & x ε₁ q₁ ∧ y ε₂ q₂}.
imports: ClassicalRealizability.Kbase ClassicalRealizability.Rationals