r = 4 (slider from 1 to 5, step 0.1)
M = (-4, 1)
c = Circle(M, r)
P = (2, 3)
a = Segment(M, P)
b = LineBisector(a)
A = Intersect(b, a)
d = Circle(A, P)
T_2, T_1 = Intersect(d, c)
t_1 = Line(P, T_1)
t_2 = Line(P, T_2)
α = Angle(t_1, t_2)
p = Line(T_1, T_2)