English
The map b.sumCoords equals the finsum over i of the coordinate functionals: (b.sumCoords) = finsum i (b.coord i).
Русский
Отображение sumCoords равно финальной сумме функционалов координат: (b.sumCoords) = finsum i (b.coord i).
LaTeX
$$$ (b.sumCoords : M \to R) = \text{finsum}_{i} (b.coord i) $$$
Lean4
theorem coe_sumCoords_eq_finsum : (b.sumCoords : M → R) = fun m => ∑ᶠ i, b.coord i m :=
by
ext m
simp only [Basis.sumCoords, Basis.coord, Finsupp.lapply_apply, LinearMap.id_coe, LinearEquiv.coe_coe,
Function.comp_apply, Finsupp.coe_lsum, LinearMap.coe_comp, finsum_eq_sum _ (b.repr m).finite_support, Finsupp.sum,
Finset.finite_toSet_toFinset, id, Finsupp.fun_support_eq]