English
If the set s coincides with t near x modulo a small exceptional set, then ContMDiffWithinAt holds for t as well.
Русский
Если множество s совпадает с t около x вне малого exceptional множества, то ContMDiffWithinAt тоже верен для t.
LaTeX
$$$ contMDiffWithinAt_congr_set' (y) (h) : ContMDiffWithinAt I I' n f s x \iff ContMDiffWithinAt I I' n f t x $$$
Lean4
protected theorem contMDiffAt (h : ContMDiffWithinAt I I' n f s x) (ht : s ∈ 𝓝 x) : ContMDiffAt I I' n f x :=
(contDiffWithinAt_localInvariantProp n).liftPropAt_of_liftPropWithinAt h ht