1. Why does the angle measure say ? (undefined) at a certain angle measure?

Question 1

2. What condition will result in the bisected angles meaure not being undefined (?)?
3. Are there conditions when it will always be '?' (undefined)

Question 2

Author- Shriranjani, IT for Change, Bengaluru
License- CC BY SA 4.0

Angle = 1.0471975511965976 rad (slider from 0 to 6.283185307179586, step 5°)
A = (5.54, 0.16)
B = (1.76, 0.14)
A' = Rotate(A, Angle, B)
α = Angle(A, B, A')
f = Ray(B, A')
g = Ray(B, A)
C = (6.16, 3.26)
c = Circle(B, C)
D = Intersect(c, f, 1)
E = Intersect(c, g, 1)
Circle = 3 (slider from 1 to 7, step 1)
d = Circle(D, Circle)
e = Circle(E, Circle)
F = Intersect(d, e, 2)
G = Intersect(d, e, 1)
h = Ray(B, G)
β = Angle(A, B, G)
γ = Angle(G, B, D)
a = false
b = false
Curve(x) = NaN
text1: "∡ABD = " + α + "
∡ABG =" + β + "
∡GBD = " + γ + ""