Education Technology

# Activities

• ##### Subject Area

• Math: Geometry: Circles

9-12

30 Minutes

• ##### Device
• TI-83 Plus Family
• TI-84 Plus
• TI-84 Plus Silver Edition
• ##### Other Materials
Students need student activity sheet.

## Opposite Angles in a Cyclic Quadrilateral

#### Activity Overview

This activity uses Cabri™ Jr. to discover that opposite angles in a cyclic quadrilateral are supplementary

#### Before the Activity

1. Draw a circle in the center of the screen. Label the center O. Use the point tool to make four points on the circle. Use the Quadrilateral Tool to construct a quadrilateral. Label the vertices A, B, C and D as in Figure 1.
2. Use the Measure Tool to measure the interior angles BAD and BCD. Label the measurements using the Alpha-numeric Tool. See Figure 2.
3. Use the Calculate Tool to find the sum of the two angles.

#### During the Activity

See attached Word .doc for details.

#### After the Activity

Correct student answers in activity sheet. Reteach as necessary.