E2.4 Explain how protractors work, use them to measure and construct angles up to 180°, and use benchmark angles to estimate the size of other angles.
Activity 1: Building Angles
Group students into pairs. Have each student construct an angle less than 180° and write the measurement on the back of the paper. Students and their partner then exchange angles. The partner measures the angle. If the measurement matches the measurement on the back of the paper, the team gets a point. The team with the most points wins.
Activity 2: How Do You Estimate the Measurement of an Angle and Measure It Using a Non-standard Unit, as Well as a Protractor and a Goniometer?
Material
- small squares of self-adhesive paper
- transparencies with various angles (large format in one copy and small format in several copies for the students)
- protractors
- giant chart entitled Angles in Ascending Order
- 11" × 17" copies of the Angles in Ascending Order (one per pair of students)
- goniometers
- dry-erase markers
- scissors
- glue stick
- small triangles with an angle of 25° (non-standard units)
- Right Angle (to print on a transparency)
- The Angles of the Sailboat
- Angles Are Everywhere
Before Learning (Warm-up)
The teacher presents students with right, straight, acute, and obtuse angles drawn on individual sheets of clear plastic. For each angle, the teacher asks students to determine whether it is straight, smaller than the right angle, or larger than the right angle. Then, the teacher asks the class to come up with a variety of strategies to put all of these angles in ascending order.
The teacher groups the students into pairs. The teacher gives each pair a sheet of white paper (27.94 cm × 43.18 cm) with a chart on it and a series of angles on a transparency. The teacher asks them to glue the angles in ascending order on the chart.
Active Learning (Exploration)
The teacher reviews the activity and has a team reproduce their completed chart on the giant Angles in the Ascending Order chart. The teacher supports students to understand the usefulness of a reference angle when comparing angles.
Consolidation of Learning
The teacher groups the students into pairs. The teacher gives each pair the Sailboat Angles activity sheet. When all the students are finished, the teacher leads a whole class discussion to compare results and draw conclusions.
Source: translated from L'@telier - Ressources pédagogiques en ligne (atelier.on.ca).