1. Introduction & Installation

2. Circles A circle is a shape with all points the same distance from the center. A circle is named by the center. The circle to the left is called circle A since the center is A. A

3. Circles The distance across a circle through the center is called the diameter. A diameter.

4. Circles The radius of a circle is the distance from the center of a circle to any point on the circle. A radius

5. Circles If you place two radii end-to-end in a circle, you would have the same length as one diameter. This means the diameter of a circle is twice as long as it’s radius. A radius 2 radii = 1 diameter

6. Circles The distance around a circle is called the circumference. A

7. Circles If you measure the distance around a circle (C or the circumference) and divide it by the distance across the circle through the center (d or the diameter), you will always come close to a particular value, depending upon the accuracy of your measurement. A

8. Circles Dividing the circumference by the diameter is a ratio represented by. This ratio is called π. Thus, for any circle, if you divide the circumference by the diameter, you get a value close to π. A

9. Pi

10. The value of π (pi) is approximately 3.14159265358979323846... We use the Greek letter (pronounced Pi) to represent this value. The number goes on forever. A

11. Pi & GeoGebra OPEN the GeoGebra PI file.

12. Pi & GeoGebra