Sometimes you just want to get the angle between the projection of two vectors in the X-Y plane. But having to use _vec set [2,0] on both of these vectors is just a waste of performance.
The difference between this command and vectorCos would be that it completely ignores the Z component (like distance2D). Very useful for faster vector operations (especially per frame operations)
vector1 vectorCos2D vector2
vector1: 2D or 3D vector (Z component is ignored)
vector2: 2D or 3D vector (Z component is ignored)
return: Number - cosine of angle between the two vectors in the X-Y plane