BD e' la differenza assoluta.

A = Point(xAxis)
B: -(A)
C = (2, 2)
a = Segment(A, C)
b = Segment(B, C)
d = Circle(C, A)
c = Line(B, C)
D, E = Intersect(d, c)
e = Segment(D, C)
f = Segment(C, E)