A little concept problem with those vectors :) Ok, so I got two objects which somehow interacts to each other, or I have two electomagnetic waves which interact in that same way. I know the angle between those two vectors, and I know lets say the result vector of that impact, the module of this isn't important for me(!), and I also know that if f,g are two vectors f+g=sqrt(f^2+g^2+2*f*g*cos(angle_between_them)). BUT THIS FORMULA ONLY GIVES ME THE MODULE OF THE RESULT VECTOR. So if I know, or I need to know whereto the result is pointing, how do I proceed. If The Above Stantment ^^^ Are a missunderstuding of a primary concept, I wouldn't be surprise :), also excuse my kinda bad english, I might have done some mistaqes up there :). Thx!