triangulo esferico

A = (-1.763348691144298, -2.9892440816214454, 0.9999999999999991)
a = Sphere(A, 2)
B = PointIn(a)
C = PointIn(a)
D = PointIn(a)
c = CircleArc(A, B, C)
d = CircleArc(A, C, D)
e = CircleArc(A, D, B)
α = Angle(B, C, D)
β = Angle(C, B, D)
γ = Angle(C, D, B)
t: α + β + γ
b = Plane(C, D, B)
f = Tangent(C, c)
g = Tangent(C, d)
δ = Angle(f, g)
h = Tangent(B, c)
i = Tangent(B, e)
j = Tangent(D, e)
k = Tangent(D, d)
l = Tangent(D, e)
m = Tangent(D, e)
n = Tangent(D, e)
ε = Angle(k, n)
ζ = Angle(h, i)
η: (-ε) - ζ + δ + α + β + γ + α + β + γ