These coordinate system are two equivalent ways of representing a vector. Use the coordinate system that is most appropriate for the problem.

Cartesian coordinates: **A**
= (A_{x},A_{y}) = A_{x} + A_{y}

Polar coordinates: **A** =
A_{r} if the vector begins
at the origin. Sometimes we write such a vector as **A** =(r,θ) Here θ is the angle
between the positive x-axis and **A**. More generally, **A** =
(A_{r},A_{θ});
* (see transparency. *

Conversion between cartesian and polar coordinates: * see transparency.*