f(x) = ℯ^(x - 1)
g(x) = cos(x)
a(x) = x > -1
A = Intersect(f, g, (0.7171847972165671, 0.7536590490862892))
h = Tangent(A, g)
i = Tangent(A, f)
α = Angle(h, i)