Education Technology

Angles formed by parallel lines and a transversal

Published on 06/09/2008

Activity Overview

Students explore relationships in various angles formed by 2 parallel lines and a transversal.

Before the Activity

Pair students and give them calculators. Get them into the Cabri application.

During the Activity

1. Draw a line. 2. Draw a line parallel to the first line. 3. Grab a line and rotate it. Notice that the lines remain parallel. 4. As you rotate the lines do you find a time when the 2 lines do not appear parallel? When does this happen? 5. Draw a third line that intersects the 2 parallel lines. This is called a transversal. (In American, but not in Scotland). 6. Observe the 3 lines. How many angles are formed? 7. Measure any 2 of the angles formed. 8. Use the calculator tool to add the 2 angle measurements. 9. Grab a point on the first parallel line and rotate the line. 10. What do you observe about the sum of the measures of the angles? 11. Confer with your partner. What do you notice about the sum of the measures of their 2 angles? 12. Make a generalization about the relationship of angles formed by a transveral intersecting 2 parallel lines. 13. Check with other people in your class. Do you find any exceptions to the rules you have made?

After the Activity

When students chose 2 angles they will either be equal in measure or supplementary. As they check with their classmates they will see these patterns. Students should copy several sets of parallel lines with a transversal and color the angles that have equal measurements the same color.