English
Same as above, restated in a form suitable for differentiation on s.
Русский
То же самое, переформулированное для дифференцирования внутри s.
LaTeX
$$$$ \\DifferentiableWithinAt 𝕜 c s x \\rightarrow \\DifferentiableWithinAt 𝕜 f s x \\rightarrow \\DifferentiableWithinAt 𝕜 (fun y => c y · f y) s x $$$$
Lean4
@[fun_prop]
theorem smul (hc : DifferentiableWithinAt 𝕜 c s x) (hf : DifferentiableWithinAt 𝕜 f s x) :
DifferentiableWithinAt 𝕜 (c • f) s x :=
(hc.hasFDerivWithinAt.smul hf.hasFDerivWithinAt).differentiableWithinAt