English
The derivative of a Fin-cons construction is obtained by combining derivatives of the head and the tail.
Русский
Производная конституции Fin.cons получается из производных головы и хвоста.
LaTeX
$$$HasDerivWithinAt\\ φ φ' s x \\land HasDerivWithinAt\\ φs φs' s x \\Rightarrow HasDerivWithinAt\\ (fun x => Fin.cons (φ x) (φs x)) (Fin.cons φ' φs') s x$$$
Lean4
nonrec theorem scomp (hg : HasDerivWithinAt g₁ g₁' t' (h x)) (hh : HasDerivWithinAt h h' s x) (hst : MapsTo h s t') :
HasDerivWithinAt (g₁ ∘ h) (h' • g₁') s x :=
hg.scomp x hh <| hh.continuousWithinAt.tendsto_nhdsWithin hst