I know in some situations you can use dot product and it's an optimization I will apply. A bit more care must be taken though. The input must be unit vectors an

I know in some situations you can use dot product and it's an optimization I will apply. A bit more care must be taken though. The input must be unit vectors and the output can be positive or negative. I tend to do my first code as logically clean and then apply optimizations later. This will likely be replaced by an `IsCusp` function instead, to make it even clearer, and provide a clean place to do the optimization.