English
If a family of differentiable sections indexed by a set I is differentiable on a set u, then the sum of these sections is differentiable on u.
Русский
Если множество секций, индексируемых, дифференцируемо на u, то их сумма дифференцируема на u.
LaTeX
$$$ MDifferentiableOn I (I.prod 𝓘(𝕜, F)) (\x => TotalSpace.mk' F x (\sum_{i} t_i x)) u$$
Lean4
theorem smul_section (hf : MDifferentiableOn I 𝓘(𝕜) f u)
(hs : MDifferentiableOn I (I.prod 𝓘(𝕜, F)) (fun x ↦ TotalSpace.mk' F x (s x)) u) :
MDifferentiableOn I (I.prod 𝓘(𝕜, F)) (fun x ↦ TotalSpace.mk' F x (f x • s x)) u := fun x₀ hx₀ ↦
.smul_section (hf x₀ hx₀) (hs x₀ hx₀)