α = 77 (slider from 0 to 90, step 1)
g = If(0 ≤ x ≤ 0.5, 1 / 4 - x^(2))
f = If(0 ≤ x ≤ tan(α * π / 180) / (1 + tan(α°)^(2)), -(1 + tan(α°)^(2)) * x^(2) + tan(α°) * x)
O = (0, 0)
O_i = (1, 0)
a = Tangent(O, f)
A = Rotate(O_i, 45*°, O)
B = Rotate(O_i, α°, O)
γ = Angle(O_i, O, B)