English
Near x, HasFPowerSeriesAt implies near 0 HasSum for ball expansions; i.e., the sum representation holds in a neighborhood.
Русский
Близко к x, HasFPowerSeriesAt влечет близко к нулю HasSum для шаровых разложений; т.е. сумма-распределение держится в окрестности.
LaTeX
$$$HasFPowerSeriesAt\\; f\\; p\\; x \\Rightarrow \\forall^\\infty y \\in 𝓝 0,\\ HasSum(\\cdot)\\, (f(x+y)).$$$
Lean4
theorem hasFPowerSeriesWithinAt (hf : HasFPowerSeriesAt f p x) : HasFPowerSeriesWithinAt f p s x :=
by
rw [← hasFPowerSeriesWithinAt_univ] at hf
apply hf.mono (subset_univ _)