Méthode des Rectangles

f(x) = x^(2)
a = Integral(f, 0, 1)
n = 5 (slider from 0 to 100, step 1)
rectSup = RectangleSum(f, 0, 1, n, 1)
rectInf = RectangleSum(f, 0, 1, n, 0)