English
Equivalently, comap m f is nontrivial exactly when the complement of the range of m is not in f.
Русский
Эквивалентно, comap m f нетривиален тогда и только тогда, когда комплемент диапазона m не принадлежит f.
LaTeX
$$$\operatorname{NeBot}(\operatorname{comap} m f) \iff (\operatorname{range}(m))^{c} \notin f$$$
Lean4
theorem comap_neBot_iff_frequently {f : Filter β} {m : α → β} : NeBot (comap m f) ↔ ∃ᶠ y in f, y ∈ range m := by
simp only [comap_neBot_iff, frequently_iff, mem_range, @and_comm (_ ∈ _), exists_exists_eq_and]