13.1 Formulation of first fundamental theorem of calculus

[AxelBoldt]

In the formulation of the first fundamental theorem of calculus in 13.1, I would write deriv (fun u ↦ ∫ x in a..u, f x) b = f b instead of deriv (fun u ↦ ∫ x : ℝ in a..u, f x) b = f b.