a: 4
fx(t) = ((t^(4) - 1) / (1 + (6 * t^(2)) + t^(4)) * a)
fy(t) = ((2 * ((t * (1 - t^(2)))) / (1 + (6 * t^(2)) + t^(4))) * a)
BL = CurveCartesian(fx(t), fy(t), t, -40, 40)
s = 6.6 (slider from -20 to 20, step 0.1)
P: (fx(s), fy(s))
Px: (s, fx(s))
Py: (s, fy(s))
b = 16
gl1:=(x^(2) + y^(2))^(2) = (b * (x^(2) - y^(2)))