English
If y ∈ 𝕜 and s and t areEventually equal outside {y} near x, then derivWithin f s x = derivWithin f t x.
Русский
Если y в 𝕜 и множества s и t в окрестности x совпадают на {y}-помещении, то derivWithin f s x = derivWithin f t x.
LaTeX
$$$$ \\ derivWithin f s x = derivWithin f t x $$$$
Lean4
theorem derivWithin_subset (st : s ⊆ t) (ht : UniqueDiffWithinAt 𝕜 s x) (h : DifferentiableWithinAt 𝕜 f t x) :
derivWithin f s x = derivWithin f t x :=
((DifferentiableWithinAt.hasDerivWithinAt h).mono st).derivWithin ht