The vectors are in 3D space: 1. It says: |Q| = 2 and |P| = 3. Angle between the vectors is 30. Find a = P - 2Q. -- So for this one, i used the angle formula cos (alpha) = (Q*P) / (|Q| * |P|) and got QP = 3sqrt(3). However i don't know how to proceed from this point on. 2. |a - b| = 22, |a| = 13 ,| b| = 19. Find |a+b| With this one i honestly don't know how to start. Edit: Ok, i drew quadrilateral, with a and b being the sides, and a+b and a-b the diagonals. I think that i might solve it.