rintro (rfl | rfl)
case mpr
x A : ℤ√(-3)
hx : 0 ≤ x.re
hA : 0 ≤ A.re
⊢ x = A ∨ x = star A → Associated' x A
case mpr.inl
x : ℤ√(-3)
hx hA : 0 ≤ x.re
⊢ Associated' x x

case mpr.inr
A : ℤ√(-3)
hA : 0 ≤ A.re
hx : 0 ≤ (star A).re
⊢ Associated' (star A) A