English
Directly asserts the derivative of Fin.cons from components is the composite derivative.
Русский
Непосредственно утверждает, что производная Fin.cons является сочетанием производных компонентов.
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
/-- Translation in the domain does not change the derivative. -/
theorem comp_const_add (a x : 𝕜) (hf : HasDerivAt f f' (a + x)) : HasDerivAt (fun x ↦ f (a + x)) f' x := by
simpa [Function.comp_def] using HasDerivAt.scomp (𝕜 := 𝕜) x hf <| hasDerivAt_id' x |>.const_add a