f

f ⁻¹

f(x) = (3 * x)
g(x) = (1 / 3 * x)
id(x) = x
a: f(2)
A = Point(f)
B = Point(g)
i = Segment(A, B)
C = Intersect(f, g, 1)
D = Point(id)
h = Line(C, D)
α = Angle(i, h)