created 08/26/97; revised 11/11/00, 07/22/03

This chapter discusses a second important vector property:
**direction**.
The previous chapter discussed the **length** of a vector.
These are the two properties that define a vector.

- Orientation of 2D vectors (represented in a particular coordinate frame).
- Ambiguity when using arc tan to calculate angle.
- Converting length and orientation into components of a column matrix.
- Radians and degrees.
- C and Java programing with arc tangent.