English
Let s1, s2 be finite sets with s1 ⊆ s2. Then the infimum over s2 of f is less than or equal to the infimum over s1 of f: s2.inf f ≤ s1.inf f.
Русский
Пусть s1, s2 — конечные множества с условием s1 ⊆ s2. Тогда инфимум над s2 от f не больше инфимума над s1 от f: s2.inf f ≤ s1.inf f.
LaTeX
$$$(s_1 \\subseteq s_2) \\implies s_2\\inf f \\le s_1\\inf f$$$
Lean4
@[gcongr]
theorem inf_mono (h : s₁ ⊆ s₂) : s₂.inf f ≤ s₁.inf f :=
Finset.le_inf (fun _ hb => inf_le (h hb))