English
If every f ∈ c satisfies f ≤ g, then sSup c ≤ g.
Русский
Если каждый f ∈ c удовлетворяет f ≤ g, то sSup c ≤ g.
LaTeX
$$$$ \\forall f\\in c, f \\le g \\implies \\mathrm{sSup}(c) \\le g. $$$$
Lean4
protected theorem sSup_le {c : Set (E →ₗ.[R] F)} (hc : DirectedOn (· ≤ ·) c) {g : E →ₗ.[R] F} (hg : ∀ f ∈ c, f ≤ g) :
LinearPMap.sSup c hc ≤ g :=
le_of_eqLocus_ge <|
sSup_le fun _ ⟨f, hf, Eq⟩ =>
Eq ▸
have : f ≤ LinearPMap.sSup c hc ⊓ g := le_inf (LinearPMap.le_sSup _ hf) (hg f hf)
this.1