Trinôme sous forme canonique
Author: Yvan Monka - m@ths et tiques 2013

a = 0.6 (slider from -10 to 10, step 0.1)
α = -1.9 (slider from -20 to 20, step 0.1)
β = -2.8 (slider from -20 to 20, step 0.1)
f(x) = a * (x - α)^(2) + β
S: (α, β)
b = OrthogonalLine(S, xAxis)
c = OrthogonalLine(S, yAxis)
A = Intersect(c, yAxis)
B = Intersect(b, xAxis)
d = Segment(A, S)
e = Segment(S, B)
texte1: "" + α + ""
texte2: "" + β + ""