Given this line M & N are two vectors which intersect and are perpendicular to each other. 1) Chose A to be orthogonal to N & M. or 2) Chose A to be perpendicular to the plane in which both M & N lie. Do the above descriptions indicate the direction of A - i.e. there are 2 possible directions. Do either of these descriptions give the direction of A? i.e. for a plane, there are 2 opposite vectors which can both be considered perpendicular to the plane. In either of these (1 & 2), does changing the order of M and N indicate a different direction?