English
Let f,g be differentiable within s at x. Then derivWithin (f + g) s x = derivWithin f s x + derivWithin g s x.
Русский
Пусть f и g дифференцируемы внутри s в x. Тогда derivWithin(f+g) s x = derivWithin f s x + derivWithin g s x.
LaTeX
$$$\text{DifferentiableWithinAt } f s x \land \text{DifferentiableWithinAt } g s x \Rightarrow \ derivWithin (f + g) s x = derivWithin f s x + derivWithin g s x$$$
Lean4
theorem derivWithin_add (hf : DifferentiableWithinAt 𝕜 f s x) (hg : DifferentiableWithinAt 𝕜 g s x) :
derivWithin (f + g) s x = derivWithin f s x + derivWithin g s x :=
derivWithin_fun_add hf hg