English
If f is continuous and f(x) ∈ slitPlane for all x, then log ∘ f is continuous.
Русский
Если f непрерывна и все значения f(x) лежат в slitPlane, то log ∘ f непрерывна.
LaTeX
$$$$\\text{Continuous } f \\Rightarrow \\text{Continuous }(\\lambda x, \\log(f x))\\text{ under slitPlane condition.}$$$$
Lean4
nonrec theorem _root_.Continuous.clog {f : α → ℂ} (h₁ : Continuous f) (h₂ : ∀ x, f x ∈ slitPlane) :
Continuous fun t => log (f t) :=
continuous_iff_continuousAt.2 fun x => h₁.continuousAt.clog (h₂ x)