O = (1.2666666666666666, 3.3)
a = 20
c = Circle(O, sqrt(a + 16))
C = Circle(O, 4)
M = (10, 4)
d = Line(O, M)
A = Intersect(C, d, 1)
B = Intersect(C, d, 2)
u = Vector(M, A)
v = Vector(M, B)
p: u * v
E = Point(C)
d' = Line(E, M)
F = Intersect(C, d', 1)
z = Vector(M, F)
w = Vector(M, E)
q: w * z
T1: " \vec{ MA } .\vec{MB}=" + p
G = If(p < a, M)
H = If(p > a, M)
T2: "\vec{MA} .\vec{MB}=" + p