p = 1.5000000000000002 (slider from 0.1 to 10, step 0.1)
c: y² = 2 p x
F: (p / 2, 0)
T_1 = Point(c)
T_2 = Point(c)
T_3 = Point(c)
t_1 = Tangent(T_1, c)
t_3 = Tangent(T_3, c)
t_2 = Tangent(T_2, c)
B = Intersect(t_3, t_1)
C = Intersect(t_1, t_2)
A = Intersect(t_3, t_2)
d = Circle(B, C, A)