English
If MDifferentiableWithinAt holds on a larger set t, then it holds on any smaller s ⊆ t.
Русский
Если MDifferentiableWithinAt верно на большем множестве t, то верно и на любом подмножестве s ⊆ t.
LaTeX
$$MDifferentiableWithinAt I I' f t x → s ⊆ t → MDifferentiableWithinAt I I' f s x$$
Lean4
theorem mono (hst : s ⊆ t) (h : MDifferentiableWithinAt I I' f t x) : MDifferentiableWithinAt I I' f s x :=
⟨ContinuousWithinAt.mono h.1 hst,
DifferentiableWithinAt.mono h.differentiableWithinAt_writtenInExtChartAt
(inter_subset_inter_left _ (preimage_mono hst))⟩