no goals
ι : Type ?u.123560
α : Type u_1
inst✝¹ : LinearOrder α
inst✝ : LocallyFiniteOrder α
a✝ b✝ a b c : α
hab : a ≤ b
hbc : b ≤ c
⊢ Ico a b ∪ Ico b c = Ico a c
rw [← coe_inj, coe_union, coe_Ico, coe_Ico, coe_Ico, Set.Ico_union_Ico_eq_Ico hab hbc]