# Activities

• • • ##### Subject Area

• Math: Geometry: Analytic Geometry
• Math: Middle Grades Math: Geometry
• Math: PreAlgebra: Geometry

• ##### Author 6-8

50 Minutes

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

## Reflections on the coordinate plane

#### Activity Overview

Use the activity center in TI-Navigator to discover a generalization for reflecting ordered pairs over the x- or y-axis.

#### Before the Activity

This activity is used to allow students to explore the coordinates of points when reflected over the x-axis or y-axis. Depending on the level of students, the teacher may have to spend extra time reviewing plotting ordered pairs. Before class, put one ordered pair on an index card for each student. The attachment is the list of ordered pairs I use, which when all are plotted, forms a sideways "V". I chose this shape because I thought it would be easy for students to see what the reflection should look like. (You can change the ordered pairs to form a picture or shape that you prefer.) Download the activity settings to allow a window for the given ordered pairs.

#### During the Activity

1) Students should go to the activity center. 2) Have students plot the ordered pair given on the index card. 3) Save the original ordered pairs on the activity screen. 4) Have students plot the reflection of their original ordered pair over the y-axis. 5) Use the cursor on the computer screen to point to original ordered pairs and then the reflected ordered pairs. 6) Select the list-graph tab and highlight the ordered pairs again. 7) Guide students to discover that the x-coordinate changes to it's opposite when reflected over the y-axis. 8) Saving all previous plots, have students plot the reflection of their original ordered pair over the x-axis. 9) Use the cursor over the ordered pairs and the list-graph tab to compare the original points to the reflected points. 10) Guide students to discover that the y-coordinate changes to it's opposite when reflected over the x-axis.

#### After the Activity

Use the Reflections LearnCheck as a quick check after the lesson or as a warm-up for the next day.