Education Technology

# Activities

• ##### Subject Area

• Math: Geometry: Transformational Geometry

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

## Dilations in the Plane (Transformations)

#### Activity Overview

In this activity, students will explore the properties of dilations and the relationships between the original and image figures.

#### 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 31 - 40 from the attached PDF file for your class
• #### During the Activity

Distribute the pages to your class.

• Construct a slider tool to generate a number in the range of approximately -4.5 to 4.5 units
• Draw a small scalene triangle on the left half of the screen and mark a point in the center of the screen
• Dilate the triangle
• Investigate the relationship between the original triangle (the pre-image) and the new triangle (the image)
• Drag a vertex of the pre-image and the center of dilations
• Observe what happens to the image
• Measure the lengths of corresponding sides, angles, and areas of the pre-image and image
• Explore different dilation factors
• #### 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