Education Technology

# Activities

• ##### Subject Area

• Math: Geometry: Triangles

9-12

90 Minutes

• ##### Device
• TI-83 Plus Family
• TI-84 Plus
• TI-84 Plus Silver Edition

TI Connect™

• ##### Accessories

TI Connectivity Cable

• ##### Other Materials
This is Activity 19 from the EXPLORATIONS Book:
Cabri™ Jr.: Interactive Geometry Activities and Investigations.

## Centers of a Triangle

#### Activity Overview

The centroid, circumcenter, orthocenter, and incenter are the four classic centers of a triangle that are studied in geometry. In this activity, you will construct these center points and discover their properties.

#### Before the Activity

• Install the Cabri Jr. App on the students' graphing calculators using TI-Connect™, a TI Connectivity Cable and the Unit-to-Unit Link Cable
• Use the TI-Navigator™ to transfer the attached Cabri Jr. AppVar files to each calculator
• See the attached PDF file for detailed instructions for this activity
• Print pages 117 - 120 from the attached PDF file for your class
• #### During the Activity

Distribute the pages to your class.

Follow the Activity procedures:

• Use the AppVar to go directly to the exploration section
• Construct a triangle and its centroid
• Construct a triangle and its circumcenter
• Construct a triangle and its orthocenter
• Construct a triangle and its incenter
• Investigate the properties of the figures drawn
• Drag the vertices and sides of the triangle and observe the changes that the figures undergo
• #### After the Activity

Review student results:

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