Occhiare i valori a e b, mentre si muove il punto A trascinandolo,
 per rendersi conto che il rapporto a/b e' costante.

r = 2 (slider from 0 to 6, step 0.1)
P = Point(xAxis)
Q = Point(xAxis)
c: (1.0 * 1.0 * 1.0 * 1.0 * 1.0 x - x(P))^(2.0) + 1.0 * 1.0 * 1.0 * 1.0 * 1.0 y^(2.0) = ((1.0 * 1.0 * 1.0 * 1.0 * 1.0 x - x(Q))^(2.0) + 1.0 * 1.0 * 1.0 * 1.0 * 1.0 y^(2.0)) * r^(2.0)
A = Point(c)
a = Segment(A, P)
b = Segment(Q, A)