f(x) = ((((x + 0.040000000000000036) * (x - 7.959999999999999)) * (x - 10.959999999999999))) / 24 - 0.12
a = 1.6 (slider from -7 to 18, step 0.1)
P_1: (a, f(a))
g = Tangent(P_1, f)
a_1 = Slope(g)
P: (a, a_1)
h = OrthogonalLine(P, xAxis)
B = Intersect(h, xAxis)
i = Segment(P, B)
f' = Derivative(f)