English
If two sections s and t are differentiable on a subset u, then their difference s - t is differentiable on u.
Русский
Если две секции s и t дифференцируемы на подмножество u, то их разность s - t дифференцируема на u.
LaTeX
$$$ MDifferentiableOn I (I.prod 𝓘(𝕜, F)) (\x => TotalSpace.mk' F x ((s - t) x)) u$$
Lean4
theorem mDifferentiableOn_sub_section (hs : MDifferentiableOn I (I.prod 𝓘(𝕜, F)) (fun x ↦ TotalSpace.mk' F x (s x)) u)
(ht : MDifferentiableOn I (I.prod 𝓘(𝕜, F)) (fun x ↦ TotalSpace.mk' F x (t x)) u) :
MDifferentiableOn I (I.prod 𝓘(𝕜, F)) (fun x ↦ TotalSpace.mk' F x ((s - t) x)) u := fun x₀ hx₀ ↦
mdifferentiableWithinAt_sub_section (hs x₀ hx₀) (ht x₀ hx₀)