## The Lesson

The radial coordinate is the first number in the pair of numbers used to describe polar coordinates. For example, in the polar coordinates**(5, 45°)**, the radial coordinate is

**5**(the number on the left):

The radial coordinate is sometimes called the radius.

## What Does the Radial Coordinate Mean?

The radial coordinate tells you how far a point is from the pole. If a point has polar coordinates**(5, 45°)**, the point would be

**5**from the pole. The image below shows what we mean by a point being 5 units from the pole:

## Using a Polar Grid to Find the Radial Coordinate

A polar grid can be used to find the radial coordinate. A polar grid is shown below:A circle is shown in red. If we read along the horizontal axis (called the polar axis), we see that this circle is labelled

**5**. This circle has a radius of 5. All points on it have a radial coordinate of

**5**.