A = (-13.986315931782979, 11.914877722871434)
B = (-5.169521794390023, -4.375755153503629)
g = Line(A, B)
P = (-11.884298786444266, -1.3395081657921508)
P' = Mirror(P, g)
f = Segment(P, P')
α = Angle(g, f)