A = (0.9999999999999998, 2.14)
α = 1.3264502315156905 rad (slider from 0 to 3.141592653589793, step 0.017453292519943295)
a_1 = 3.1 (slider from 0 to 5, step 0.1)
B = Point(Circle[A, a_1])
a = Segment(A, B)
D = Rotate(B, α, A)
β = Angle(B, A, D)
k1 = Circle(B, A)
k2 = Circle(D, A)
C = Intersect(k1, k2, 2)
c = Segment(D, C)
b = Segment(C, B)
d = Segment(D, A)