sin(α) \; = \;  \;  \frac{ AC }{BC } 

cos(α) \; = \;  \frac{ AB }{BC } 

B = (-3.3242049586776834, -0.49569586776859587)
C = (4.525395041322319, -0.4428958677685958)
a = Segment(B, C)
c = Semicircle(B, C)
A = Point(c)
b = Segment(A, B)
d = Segment(A, C)
α = Angle(C, B, A)
β = Angle(B, A, C)
đa giác1, c_1, a_1, b_1 = Polygon(A, B, C)