h = 0.5 (slider from 0.5 to 2, step 0.1)
f(x) = 1.0 / 2.0 * x^(3.0) - 2.0 * x + 2.0
A = Point(f)
B: (0.4 + h, f(0.4 + h))
a = Line(A, B)