# Activities

• • • ##### Subject Area

• Math: Geometry: Analytic Geometry

• ##### Author 9-12

15 Minutes

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

## What is a linear pair?

#### Activity Overview

Use Cabri to investigate relationship of linear pairs.

#### Before the Activity

Group students in pairs. Give the students calculators

#### During the Activity

1. Draw a line using Cabri. 2. Draw a second line using the first point in the construction of the first line. 3. Label a point of the first line A, label a point on the second line B, label a point on the other side of the intersection on the first line C, Label the point of intersection D. 4. Use the measurement tool to measure angle ADB and angle BDC. 5. Use the calculate tool to add measures of angel ADB and Angle BDC. 6. What is the sum of angle ADB and angle BDC? 7. Grab the second point of the first line, the second point that you used to construct the line. 8. Rotate the first line about the point of intersection of the 2 lines. 9. What do you notice about the sum of the angles? 10. These are called linear pairs. Why do you like they are called linear pairs? What is the sum of the angles in a linear pair? 11. Record 5 linear pairs of angles in your notebook. 12. Write the definition of linear pair in your notebook.

#### After the Activity

After this activity I ask the students to record the definition of linear pair and to explain why it is called a linear pair. I ask them to record several sets of angle measures that are linear pairs.