English
If F reflects the cospan limit and F is faithful, then an IsPullback for F.map f,g,h,i implies IsPullback f,g,h,i.
Русский
Если F отражает предел для cospan и F верен, то IsPullback для отображений F.map f,... подразумевает IsPullback f,...
LaTeX
$$$ [\\operatorname{ReflectsLimit}(\\mathrm{cospan}(h,i)) F] [F.Faithful] (H : \\operatorname{IsPullback}(F.map f,F.map g,F.map h,F.map i)) : \\operatorname{IsPullback}(f,g,h,i) $$$
Lean4
theorem of_map_of_faithful [ReflectsColimit (span f g) F] [F.Faithful]
(H : IsPushout (F.map f) (F.map g) (F.map h) (F.map i)) : IsPushout f g h i :=
H.of_map F (F.map_injective <| by simpa only [F.map_comp] using H.w)