Activity Overview
In this activity, students will learn the basic concepts of the circle. They explore the relationship between the diameter and the radius, and between the diameter and circumference of a circle. They also get familiar with the Greek symbol π (pi).
Before the Activity
Install the Cabri™: Jr. App on the students' graphing calculators using one of these two methods:
TI-Connect™, a TI Connectivity Cable, and the Unit-to-Unit Link Cable
TI-Navigator™ "send to class" feature
See the attached PDF file for detailed instructions for this activity
Print pages 65 - 67 from the attached PDF file for your class
During the Activity
Distribute the pages to the class.
Follow the Activity procedures:
Construct a circle
Draw the radius by constructing a segment from a point on the circle to the center of the circle
Construct the diameter by drawing a segment from a point on the circle to another point on the circle, and passing through the center
Measure the length of the radius and the diameter
Observe that the length of the radius is half the length of the diameter
Alter the circle and verify the relationship
Calculate the circumference of the circle
Calculate the ratio of the circumference to the diameter, and observe that the ratio is equal to π (pi) or 3.14
Calculate the circumference and radius for other circles and examine the ratios
Note that of any circle, circumference is equal to π (pi) times diameter and also equal to 2 radii times π (pi)
After the Activity
Review student results:
As a class, discuss questions that appeared to be more challenging
Re-teach concepts as necessary