Me encanta 
la braquistocrona

a = 1
b = CurveCartesian(a * (t + sin(t)), a * (1.0 - cos(t)), t, 3.141592653589793, 6.28319)
A = Point(b)
c = Tangent(A, b)
d = OrthogonalLine(A, c)
B = Point(d)
u = Vector(A, B)
v = UnitVector(u)
C: A + 0.05 * v
e = Circle(C, A)