A_1 = (2.48, 4.84)
B_1 = (7.84, -3.12)
g = Line(A_1, B_1)
A = (1.28, 2.32)
b = OrthogonalLine(A, g)
D = Intersect(g, b)
α = 0.8203047484373349 rad (slider from 0 to 3.141592653589793, step 0.017453292519943295)
D' = Rotate(D, -1.0 * (α - 90.0 * °), A)
β = Angle(D', A, D)
c = Line(A, D')
B = Intersect(c, g)
d = Segment(A, B)
α_1 = Angle(A, B, B_1)