⊢ (let s := sqrt 0;
    if 0 - s * s < s then (0 - s * s, s) else (s, 0 - s * s - s)) =
    0
⊢ unpair 0 = 0
rw [unpair]
no goals
⊢ (let s := sqrt 0;
    if 0 - s * s < s then (0 - s * s, s) else (s, 0 - s * s - s)) =
    0
simp