f = Function(1.0 / 6.0 * x^(3.0) - 1.0 / 2.0 * x^(2.0) - x, -3.0, 5.0)
a = 3.2 (slider from -3 to 5, step 0.1)
A: (a, f(a))
b = Tangent(A, f)
c = Slope(b)
B: (a, c)