Rectangular components of a vector: a = ax + ay + az. Cartesian unit vectors: in 3-d, the set of cartesian unit vectors i, j, k, is used to designate the direction of the x, y, z axes, respectively. They can be positive or negative depending on their directions along the axes: magnitude of a cartesian vector, coordinate direction angles: the direction of a is defined by the coordinate direction angles (alpha), (beta), and (cid:0) (gamma), measured between the tail of a and the positive x, y, z axes provided that they are located at the tail of a. These numbers are known as the direction cosines of a: one way to obtain the direction cosines is to form the unit vector ua in the direction of a. where a = ( ax. 2: one way to check if all the three angles are correct. The following equation can be used. o: transverse and azmuth angles.