t = 5 (slider from 0 to 20, step 0.1)
C: (cos(0.25 * t), sin(0.25 * t))
A = (0, 0)
c = Circle(A, C)
f(x) = cos(0.25 * x)
g(x) = sin(0.25 * x)
E: (t, cos(0.25 * t))
D: (t, sin(0.25 * t))