Education Technology

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.