English
If the two left and right endpoints satisfy compatibility conditions, the union of Ico(a,b) and Ico(c,d) equals Ico(min(a,c), max(b,d)).
Русский
Если крайние точки интервальных отрезков совместимы, то объединение Ico(a,b) и Ico(c,d) равно Ico(min(a,c), max(b,d)).
LaTeX
$$$ Ico(a,b) \cup Ico(c,d) = Ico(\min(a,c), \max(b,d)) $ under suitable compatibility conditions.$$
Lean4
theorem Ico_union_Ico_eq_Ico {a b c : α} (hab : a ≤ b) (hbc : b ≤ c) : Ico a b ∪ Ico b c = Ico a c := by
rw [← coe_inj, coe_union, coe_Ico, coe_Ico, coe_Ico, Set.Ico_union_Ico_eq_Ico hab hbc]