English
If g and f are continuous on a set s, then x ↦ g(x) ∘ f(x) is continuous on s.
Русский
Если g и f непрерывны на s, то композиция g(x) ∘ f(x) непрерывна на s.
LaTeX
$$$\\text{ContinuousOn } g\,s \\to \\text{ContinuousOn } f\,s \\Rightarrow \\text{ContinuousOn } (x \\mapsto g(x)\\circ f(x))\,s$$$
Lean4
theorem _root_.ContinuousOn.compCM (hg : ContinuousOn g s) (hf : ContinuousOn f s) :
ContinuousOn (fun x ↦ (g x).comp (f x)) s := fun a ha ↦ (hg a ha).compCM (hf a ha)