English
Same as above: the derivative of a sum under HasDerivAtFilter is the sum of derivatives.
Русский
То же самое: производная суммы равна сумме производных в рамках HasDerivAtFilter.
LaTeX
$$$\text{HasDerivAtFilter} (f+g) (f'+g') x L$ given $\text{HasDerivAtFilter} f f' x L$ and $\text{HasDerivAtFilter} g g' x L$$$
Lean4
nonrec theorem add (hf : HasDerivAtFilter f f' x L) (hg : HasDerivAtFilter g g' x L) :
HasDerivAtFilter (f + g) (f' + g') x L := by simpa using (hf.add hg).hasDerivAtFilter