English
If f is C^n, then its tangent map is C^m: the smoothness lifts to tangent level.
Русский
Если f гладкое, то tangentMap гладко в касательном уровне.
LaTeX
$$$\forall hf : ContMDiff I I' n f,\ hmn : m + 1 ≤ n \Rightarrow ContMDiff I.tangent I'.tangent m (tangentMap I I' f)$$$
Lean4
/-- If a function is `C^n`, with `1 ≤ n`, then its bundled derivative is continuous. -/
theorem continuous_tangentMap (hf : ContMDiff I I' n f) (hmn : 1 ≤ n) : Continuous (tangentMap I I' f) :=
by
rw [← contMDiffOn_univ] at hf
rw [← continuousOn_univ]
convert hf.continuousOn_tangentMapWithin hmn uniqueMDiffOn_univ
rw [tangentMapWithin_univ]