English
Restriction to the complement of the range of extend f g g' equals g' composed with the projection to the original domain.
Русский
Ограничение дополнения к диапазону extend даёт функцию g' после проекции на исходную область.
LaTeX
$$$(\\operatorname{range} f)^{c}.restrict (\\operatorname{extend} f g g') = g' \\circ \\operatorname{Subtype.val}$$$
Lean4
@[simp]
theorem restrict_extend_compl_range (f : α → β) (g : α → γ) (g' : β → γ) :
(range f)ᶜ.restrict (extend f g g') = g' ∘ Subtype.val := by classical exact restrict_dite_compl _ _