Relation between two dimensional (2D) and three dimensional (3D) angles

If the angles are given in two dimensional (2D) form but they needs to be represented in three dimensional (3D) form, then the relation between 2D and 3D angles need to be established. This is important in resolving the forces of tower cables, anchor blocks with horizontal and vertical bends etc. This video establish the relation between 2D and 3D angles verify it with the help of direction cosines formula.