English
For any p = (f,g) in E×E, ContDiffAt Real n (p ↦ ⟪f,g⟫) at p holds if f and g are ContDiffAt Real n at the corresponding entries.
Русский
Для любого p = (f,g) в E×E верно ContDiffAt Real n для отображения p ↦ ⟪f,g⟫, если f и g имеют ContDiffAt Real n на точке p.
LaTeX
$$$\\operatorname{ContDiffAt}_{\\mathbb{R}} n\\bigl(p \\mapsto \\langle p_1, p_2\\rangle\\bigr)(p).$$$
Lean4
theorem contDiffAt_inner {p : E × E} {n} : ContDiffAt ℝ n (fun p : E × E => ⟪p.1, p.2⟫) p :=
ContDiff.contDiffAt contDiff_inner