English
If f and g are continuous on a set s, then z ↦ f(z)(g(z)) is continuous on s.
Русский
Если f и g непрерывны на множество s, то зета отображение f(z) на g(z) непрерывно на s.
LaTeX
$$$\\text{ContinuousOn } f s \\Rightarrow \\text{ContinuousOn } g s \\Rightarrow \\text{ContinuousOn } (\\lambda z. f(z)(g(z))) s$$
Lean4
protected theorem eval (hf : ContinuousOn f s) (hg : ContinuousOn g s) : ContinuousOn (fun z ↦ f z (g z)) s :=
fun z hz ↦ (hf z hz).eval (hg z hz)