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A circle is a set of points that are at the same distance from a
fixed point called the centre of the circle.
Parts of a Circle
The parts of a circle are given special names as described below:
- The radius, r, of a circle is the distance from its
centre to a point on the edge of the circle.
- The diameter, d, of a circle is the distance across the
circle through its centre.
In symbolic form:
So, the radius is half of the diameter.
Example 11
Find the diameter of the following circle:
Solution:
So, the diameter of the circle is 16 cm.
Example 12
Find the radius of the following circle:
Solution:
So, the radius of the circle is 12 cm.
Key Terms
radius, diameter
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