Chiều quay âm

α = 1.064650843716541 rad (slider from 0 to 6.283185307179586, step 0.017453292519943295)
O = (13.546497979552376, 5.670995983938551)
M = (21.04882138693443, 5.638658383044661)
d = Segment(O, M)
M' = Rotate(M, -(α), O)
e = Segment(O, M')
f = CircleArc(O, M', M)
γ = Angle(M', O, M)