Integrale_expo_rectangle

n = 6 (slider from 1 to 500, step 1)
f(x) = If[0 ≤ x ≤ 1, exp(x)]
T_n = LowerSum(f, 0, 1, n)
S_n = UpperSum(f, 0, 1, n)
texte2: "S_n = " + S_n + ""
A: S_n - T_n
texte1: "T_n = " + T_n + ""
A_n = RectangleSum(f, 0, 1, n, 0.5)