English
If f is continuous on the closed interval uIcc[a,b], then f(uIcc[a,b]) is the closed interval between the infimum and supremum of the image.
Русский
Если f непрерывна на uIcc[a,b], то образ f(uIcc[a,b]) есть замкнутый интервал между sInf и sSup образа.
LaTeX
$$$f''\\mathrm{uIcc}(a,b) = \\mathrm{Icc}(sInf(f''\\mathrm{uIcc}(a,b)), sSup(f''\\mathrm{uIcc}(a,b)))$$$
Lean4
theorem image_uIcc_eq_Icc (h : ContinuousOn f [[a, b]]) :
f '' [[a, b]] = Icc (sInf (f '' [[a, b]])) (sSup (f '' [[a, b]])) :=
image_Icc min_le_max h