English
If f is analytic on a neighborhood of a subset s, then exp(f) is analytic on that same neighborhood.
Русский
Если f аналитична на окрестности множества s, то e^{f} аналитична на той же окрестности.
LaTeX
$$$ \\operatorname{AnalyticOnNhd}_{\\mathbb{C}}(f;s) \\Rightarrow \\operatorname{AnalyticOnNhd}_{\\mathbb{C}}(\\exp \\circ f;s)$$$
Lean4
/-- `exp ∘ f` is analytic -/
theorem «cexp» (fs : AnalyticOnNhd ℂ f s) : AnalyticOnNhd ℂ (fun z ↦ exp (f z)) s := fun z n ↦
analyticAt_cexp.comp (fs z n)