α_1 = 0 rad (slider from 0 to 1.5707963267948966, step 0.017453292519943295)
f(x) = -5 * x^(2) / (58.5 * cos(α_1)^(2)) + x * tan(α_1) + 2.1
A = Point(f)
a = OrthogonalLine(A, yAxis)
B = Point(a)
B' = Rotate(B, α_1, A)
v = Vector(A, B')
b = Segment(A, B')
g = Function(f, 0, 5)