f(x) = sqrt(4.0 * x^(2.0) * (4.0 - x^(2.0)))
g(x) = -sqrt(4.0 * x^(2.0) * (4.0 - x^(2.0)))
t = 0.2 (slider from -10 to 10, step 0.1)
P: (2.0 * cos(t), 4.0 * sin(2.0 * t))
O = (0, 0)
P_1: (-(2.0) * cos(t), -(4.0) * sin(2.0 * t))
a = Segment(P, P_1)