Tangente à un cercle
Author: m@ths et tiques 2012

A = (1.9143688242681265, 1.4888956792916488)
B = (5.06, 2.3)
c = Circle(A, B)
C = Point(c)
a = Segment(A, C)
b = OrthogonalLine(C, a)
D = Point(b)
α = Angle(A, C, D)