English
In a Boolean algebra, the complement of liminf equals the limsup of complements.
Русский
В булевой алгебре комплемент лиминфа равен лимсупу комплементов.
LaTeX
$$$(\\liminf u f)^c = \\limsup (compl \\circ u) f$$$
Lean4
/-- In other words, `liminf cofinite s` is the set of elements lying outside the family `s`
finitely often. -/
theorem liminf_set_eq : liminf s cofinite = {x | {n | x ∉ s n}.Finite} := by
simp only [← cofinite.bliminf_true s, cofinite.bliminf_set_eq, true_and]