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:
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
The Radial Coordinate Can Only Be Positive
The radial coordinate can only be a positive numbers
(0, 1, 2, 3...).
It does not matter which direction a point is from a point, the distance is positive.