`Base.angle`

— Method`angle(point1::T, point2::T) where {T}`

Accurately ascertains the undirected angle (0 <= radians < pi) between two points given in N-dimensional Cartesian coordinates.

Prefer this to `acos`

alternatives

- more reliably accurate
- more consistently stable

Suggested when any |coordinate| of either point may be outside 2^±20 or [1/1*000*000, 1*000*000]. Strongly recommended when any |coordinate| is outside 2^±24 or [1/16*000*000, 16*000*000].

If one of the points is at the origin, the result is zero.

You *must* define a tuple constructor `Tuple(x::YourPointType) = ...`

if one does not already exist.