Direction
The set of all lines parallel to a given line d.
The term direction is also used in the sense of the orientation of a straight line in the plane.
Properties
- Two or more lines belong to the same direction if they are parallel to each other.
- On any line representing a given direction, there are two directions of travel.
- Through a point P of the plane pass an infinity of lines; each of them belongs to a different direction. Only one of these lines passes through a point Q other than P and this line defines the direction PQ.
Notation
The direction of a line d is denoted dir(d).Exemple
dir(d)