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 4 from the EXPLORATIONS Book:
Exploring Mathematics with Cabri™ Jr. Application

## Angles of a Triangle

#### Activity Overview

In this activity, students will measure angles and investigate the relationships between interior and exterior angles of a triangle. They understand the definition of interior angles, exterior angles, adjacent angles, supplementary angles, and remote interior angles.

#### 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 cables
• See the attached PDF file for detailed instructions for this activity
• Print pages 45 - 52 from the attached PDF file for your class
• #### During the Activity

Distribute the pages to your class.

• Draw a triangle to fill most of the screen
• Measure the three interior angles
• Calculate the sum of the interior angles
• Drag a vertex of an angle and observe what happens to the angle measures and their sum
• Construct a line on one side of the triangle
• Construct and label a point on the line to the right of the triangle
• Measure the exterior angle, adjacent interior angle, and the two remote interior angles
• Understand the relationship between exterior angles and the interior angles
• #### After the Activity

Students will fill in the Data Collection and Analysis sheet.

Review student results:

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