English
If f and g are maximal on s at a, then their minimum is also maximal at a.
Русский
Если f и g максимальны на s в a, то их минимум максимален в a.
LaTeX
$$$\\mathrm{IsMaxOn}(f,s,a) \\land \\mathrm{IsMaxOn}(g,s,a) \\Rightarrow \\mathrm{IsMaxOn}(\\lambda x. \\min\\{f(x),g(x)\\}, s, a)$$$
Lean4
theorem min (hf : IsMaxOn f s a) (hg : IsMaxOn g s a) : IsMaxOn (fun x => min (f x) (g x)) s a :=
IsMaxFilter.min hf hg