Radial Coordinates
(KS2, Year 6)

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.

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.

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See Also

What is a circle? What is a radius?