get-interface-rotation

function getInterfaceRotation(a: number[], b: number[]): number

Returns the rotation angle (-𝜋 <= θ <= 𝜋 guaranteed) from some vector to another vector considering them to both start at the same point.

If one of the vectors is the zero vector then 0 is returned.

It can also be imagined that the 2nd vector starts where the 1st one ends.

Intermediate calculations are done in double precision in a numerically stable manner.

Name	Type	Description
`a`	number[]	the first 2d vector given as `[x,y]` where `x` and `y` are the coordinates, e.g. `[2,3]`
`b`	number[]	the second 2d vector