English
The range of lmap f equals the comap of the pi-submodule of the ranges of f_i.
Русский
Образ lmap f равен прообразу пи-подмодуля диапазонов f_i.
LaTeX
$$$\\mathrm{range}(\\mathrm{lmap}\\ f) = \\big(\\mathrm{Submodule.pi}(\\mathrm{Set.univ}, i \\mapsto \\mathrm{range}(f_i))\\big).\\mathrm{comap}(\\mathrm{DirectSum.coeFnLinearMap}\\,R).$$$
Lean4
theorem range_lmap :
LinearMap.range (lmap f) =
(Submodule.pi Set.univ (fun i ↦ LinearMap.range (f i))).comap (DirectSum.coeFnLinearMap R) :=
DFinsupp.range_mapRangeLinearMap f