cardioide parametriche
a = 2 (modificabile)

x = a*(2 cos(t)- cos(2t))
y =a*(2 sin(t) - sin(2t))

a = 1 (slider from -5 to 5, step 0.1)
b = CurveCartesian(a * (2 * cos(t) - cos(2 * t)), a * (2 * sin(t) - sin(2 * t)), t, 0, 6.28)