English
The Set form of splitUpper is I.toSet ∩ {y | x < y_i}.
Русский
Множество-форма splitUpper: I.toSet ∩ {y | x < y_i}.
LaTeX
$$$(splitUpper I i x) = I^{\\;toSet} \\cap \\{ y : x < y_i \\}$$$
Lean4
@[simp]
theorem coe_splitUpper : (splitUpper I i x : Set (ι → ℝ)) = ↑I ∩ {y | x < y i} := by
classical
rw [splitUpper, coe_mk']
ext y
simp only [mem_univ_pi, mem_Ioc, mem_inter_iff, mem_coe, mem_setOf_eq, forall_and,
forall_update_iff I.lower fun j z => z < y j, max_lt_iff, and_assoc (a := x < y i),
and_forall_ne (p := fun j => lower I j < y j) i, mem_def]
exact and_comm