A = (1.66265453800316, 2.6801978647435547, 0)
B = (8, 2, 0)
C = Point(Circle[Midpoint[A, B], (Distance[A, B] * sqrt(3) / 2), Segment[A, B]])
a, D, tahkoABC, tahkoACD, tahkoABD, tahkoBCD, särmäAC, särmäAB, särmäBC, särmäAD, särmäCD, särmäBD = Tetrahedron(A, B, C)
E = Midpoint(C, B)
f = Segment(A, E)
α = Angle(E, A, D)
g = Segment(D, E)
β = Angle(D, E, A)
D': (x(D), y(D), 0)
h = Segment(D, D')