intro imp
case mp
x : ℝ × ℝ
⊢ (∀ (i : ℝ), 0 ≤ i → i ≤ 1 → (i, 0) ≤ x ∧ x ≤ (1, i)) → x ∈ Set.singleton (1, 0)
case mp
x : ℝ × ℝ
imp : ∀ (i : ℝ), 0 ≤ i → i ≤ 1 → (i, 0) ≤ x ∧ x ≤ (1, i)
⊢ x ∈ Set.singleton (1, 0)