b = 0 (slider from 0 to 99, step 1)
c: floor(b / 10.0) + 1.0
d: b - (c - 1.0) * 10.0 + 1.0
B = Intersect(xAxis, yAxis)
A: (c, d)
a = Segment(B, A)
α = Angle(xAxis, a)