English
If f is continuous within s at a, then arsinh ∘ f is continuous within s at a.
Русский
Если f непрерывна внутри s в точке a, то arsinh(f) непрерывна внутри s в a.
LaTeX
$$$\\forall X\\ {\\text{topological space}},\\ f:\\,X \\to \\mathbb{R},\\ s:\\,\\text{Set }X,\\ a:\\,X,\\ (\\operatorname{ContinuousWithinAt} f s a)\\Rightarrow \\operatorname{ContinuousWithinAt}(\\lambda x. \\operatorname{arsinh}(f x)) s a.$$$
Lean4
nonrec theorem arsinh (h : ContinuousWithinAt f s a) : ContinuousWithinAt (fun x => arsinh (f x)) s a :=
h.arsinh