Hi all, I am looking for some help please. I want to calculate the signed angle between two 3D (x,y,z) vectors. I know the formula to find the unsigned angle; angle = arccos(A.B / |A||B|) but how do I get the signed angle? From searching through the internet it seems that there isnt an obvious/easy solution ? To clarify: Assume the two vectors can lie on any plane. Taking the first vector as a reference I want to know the angle that I would need to rotate the first vector to line it up with the second vector. Can someone more clever than me point me in the right direction, or prehaps offer a solution please ?