a = 2.4 (slider from 0 to 5, step 0.1)
F_1 = (0.6495016883683018, -0.5385364019044985)
C = Circle(F_1, 2.0 * a)
F_2 = (4.198652000336531, -0.5736765040031938)
P = Point(C)
b = Segment(P, F_1)
d = LineBisector(P, F_2)
M = Intersect(d, b)
C' = Circle(M, F_2)
f = Segment(M, F_2)
g = Segment(F_1, F_2)