A_1 = (8.401439728481595, -2.1586983830274695)
B_1 = (29.173935315386203, -2.0474668136196805)
A = (12.739470935385363, 4.098077396160661)
B = (10.431415870173742, -1.6581563206924188)
C = (22.221962227399374, -1.5747326436365772)
đa giác1, c, a, b = Polygon(A, B, C)
d = LineBisector(a)
D = Midpoint(a)
e = Segment(B, D)
f = Segment(D, C)
E = Point(d)
α = Angle(C, D, E)