# Classroom Activities

• ##### Subject Area

• Math: Geometry: Circles
• Math: Geometry: Quadrilaterals and Polygons

9-12

60 Minutes

• ##### Device
• TI-89 / TI-89 Titanium
• TI-92 Plus / Voyage™ 200

TI Connect™

• ##### Accessories

TI Connectivity Cable

• ##### Report an Issue

Circles: Circumference and Area

Published on 07/19/2006

#### Activity Overview

The idea of perimeter can be applied not only to polygons but to circles as well. The same idea can be said for the area of a circle.

#### Before the Activity

In trying to see the relationship that exists between the area of a polygon and a circle, imagine a circle that has been cut into triangles and placed in a regular fashion, one next to the other.
See the attached Activity PDF file(s) for detailed instructions for this activity.
Install the Cabri Geometry™ App on the students' graphing calculators following the attached instructions.

#### During the Activity

Follow the procedures outlined in the activity.
Students will:

• Be able to use the graphing calculator and Cabri Geometry to understand the area and circumference of circles and the area and perimeter of a regular polygon.
• #### After the Activity

• Review student results:
• As a class, discuss questions that appeared to be more challenging
• Re-teach concepts as necessary