α

α = 1.23 (slider from 0 to π / 2, step 0.01)
V = 30 (slider from 0 to 50, step 1)
a: ((0.2 * V) * sin(α))
h(t) = If[0 ≤ t ≤ a, (-5 * t^(2)) + ((V * t) * sin(α))]
d(t) = If[0 ≤ t ≤ a, ((V * t) * cos(α))]
w: (0, 1)
v: (1, 0)
O = Point(v)
M = CurveCartesian((d(t), h(t)), t, -10, 10)
u: (d'(0), h'(0))
A: (d(a), 0)
T: O + u
β = Angle(A, O, T)