# Definition:Polar Coordinates/Angular Coordinate

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## Definition

Let $P$ be a point in a system of polar coordinates where $O$ is the pole.

The angle measured anticlockwise from the polar axis to $OP$ is called the **angular coordinate** of $P$, and usually labelled $\theta$.

If the angle is measured clockwise from the polar axis to $OP$, its value is considered negative.

## Also known as

The **angular coordinate** in a system of polar coordinates is also known as the **polar angle**, or **azimuth**.

Other words that can be seen to mean the same thing are:

**amplitude****anomaly****vectorial angle****inclination**.

Beware the term **azimuth**, as it is used in astronomy in a similar but significantly different way, to mean the angle measured clockwise from north.

Sometimes south is used.

## Also see

## Sources

- 1933: D.M.Y. Sommerville:
*Analytical Conics*(3rd ed.) ... (previous) ... (next): Chapter $\text I$. Coordinates: $2$. Coordinates - 1968: Murray R. Spiegel:
*Mathematical Handbook of Formulas and Tables*... (previous) ... (next): $\S 5$: Trigonometric Functions - 1998: David Nelson:
*The Penguin Dictionary of Mathematics*(2nd ed.) ... (previous) ... (next):**azimuth**:**1.** - 2008: David Nelson:
*The Penguin Dictionary of Mathematics*(4th ed.) ... (previous) ... (next):**azimuth**:**1.**