Winkel sichtbar:

A = (-4, 0)
B = (6, 0)
a = Line(A, B)
C = (2, 4)
D = (9, 3)
E = Point(a)
b = Segment(C, E)
c = Segment(E, D)
Lot = OrthogonalLine(E, a)
α = Angle(Lot, c)
F = Point(Lot)
d = Segment(F, E)
β = Angle(F, E, C)
s: b + c
Text1: "b + c  =  " + s
e = true