The vectors e 1 and e2 of non-* * lines are called a set of bases of all vectors on this plane. Usually based on two vectors with the same x and y directions! (Cardinality cannot be a zero vector)

trait

The 1. base is a vector with two non-* * lines. 2. The choice of base is not unique. The non-* * line of two vectors in a plane is the condition that these two vectors can be used as a set of bases of all vectors in this plane.