English
The complex exponential function exp: ℂ → ℂ is continuous on the entire plane.
Русский
Функция экспоненты exp: ℂ → ℂ непрерывна на всей плоскости.
LaTeX
$$$$ \\exp: \\mathbb{C} \\to \\mathbb{C} \\quad \\text{is continuous on } \\mathbb{C}. $$$$
Lean4
@[continuity]
theorem continuous_exp : Continuous exp :=
continuous_iff_continuousAt.mpr fun x =>
continuousAt_of_locally_lipschitz zero_lt_one (2 * ‖exp x‖)
(fun y ↦ by
convert locally_lipschitz_exp zero_le_one le_rfl x y using 2
congr
ring)