First, you need to be very sure that you understand that thedot product of two vectors is aand not an angle. For unit vectors that number is the cosine of the angle between the vectors. If it is positive the angle is acute; if it is negative the angle is obtuse; if it is zero the angle is a right angle. As to you actual question, what does adding the cosines of any two angles with a common ray mean? Surely that are many different possible meanings.number