Section Scal_l.
Context {K : AbsRing} {V : NormedModule K}.
End Scal_l.

Lemma Derive_div (f g : R -> R) (x : R) :
ex_derive f x -> ex_derive g x -> g x <> 0
-> Derive (fun y => f y / g y) x = (Derive f x * g x - f x * Derive g x) / (g x) ^ 2.