A = (0, 0)
c = Circle(A, sqrt(2))
a = 0.5577087449526965 (slider from 0 to 1)
B = Point(c)
b = 0.9516988526771992 (slider from a to 1)
C = Point(c)
d = CircleSector(A, C, B)
AS: (sqrt(a^(2) - b^(2) + 1), sqrt((-a^(2)) + b^(2) + 1))
AL: (sqrt(a^(2) + b^(2) - 1), sqrt((-a^(2)) - b^(2) + 3))
US: (b, sqrt(2 - b^(2)))
UL: (a, sqrt(2 - a^(2)))