1. Lesson Objectives 1.You will gain a deeper understanding of the concept of diameter and radius. 2.You will explain the definition of a circle. 3.You will identify and measure the diameter and radius of a circle. 4.You will demonstrate that the diameter of the circle is twice the size of the radius of a circle. 5.You will demonstrate that the radius is one half the diameter.

2. Diameter & Radius of Circle Developed by Ivan Seneviratne

3. The Diameter The distance across a circle through the center is called the diameter. It is the longest distance across a circle. The diameter cuts through the center of the circle. This is what makes it the longest distance. A Diameter d = 2 x r The Diameter is twice the size of the radius of a circle. This relationship is expressed in the following formula where the diameter is d and radius is r.

4. Measuring Diameter How do you measure the diameter of a circle without a given centre point ?

5. Radius The radius of a circle is the distance from the center of the circle to the outside edge. A radii If you place two radii end- to-end in a circle, you would have the same length as one diameter. This relationship is expressed in the following formula where the radius is r an diameter is d. r = d/2

6. Conclusion 1.The diameter of a circle is twice as long as the radius. 2.The radius is one half the diameter. 3.Diameters and radii are measured in linear units, such as inches and centimeters.

7. This presentation is developed by Ivan Seneviratne © 2007 purely for personal use. ivanthexplorer@yahoo.co.uk