(** Subtraction *)

Lemma Lim_minus (f g : R -> R) (x : Rbar) :
ex_lim f x -> ex_lim g x ->
ex_Rbar_minus (Lim f x) (Lim g x) ->
Lim (fun y => f y - g y) x = Rbar_minus (Lim f x) (Lim g x).