English
If s is a subsingleton, then HasConstantSpeedOnWith f s l holds for any l (the speed is vacuously defined).
Русский
Если s подклетно, то HasConstantSpeedOnWith f s l выполняется для любого l (скорость тождественна нулю).
LaTeX
$$HasConstantSpeedOnWith f s l if s.Subsingleton$$
Lean4
theorem hasConstantSpeedOnWith_of_subsingleton (f : ℝ → E) {s : Set ℝ} (hs : s.Subsingleton) (l : ℝ≥0) :
HasConstantSpeedOnWith f s l := by
rintro x hx y hy; cases hs hx hy
rw [eVariationOn.subsingleton f (fun y hy z hz => hs hy.1 hz.1 : (s ∩ Icc x x).Subsingleton)]
simp only [sub_self, mul_zero, ENNReal.ofReal_zero]