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This lesson will involve two activities: the construction of a "Paper Protractor" and an
"Angle Comparison Strip."1 The main purpose
of both these projects is to improve students'
ability to estimate and compare angle measurements. These skills will make later instruction on triangles, protractors, rotations,
and other topics more effective.
Materials for the
Introduction to the Rotating “Paper Protractor”
Introduce the first project to students by simply asking, “What are angles?” Good responses to elicit are “angles are two connected lines,” or “angles are corners.” Draw some examples on the board and show students how to use a paper protractor (constructed beforehand by the teacher) to estimate angle sizes. For instance:
Also, teach students that the size of an angle depends on how opened or closed it is, not how long its lines are.
Next, using the paper protractor (or the teacher’s previously constructed “Angle Comparison Strip”), the teacher should focus student attention on landmark angles, namely 60, 90, 180, and 360 degrees. Point out to students that the lines of a 90 degree angle can also be called “perpendicular” lines. Also, show them that a 180 degree angle is when two lines open up to the point of forming a straight line. A 360 degree angle is an angle that has opened up so much that it has closed back on itself, making it look a lot like a 0 degree angle. To really help students remember these landmarks, the teacher or a student volunteer could perform a 180 and/or 360 degree “spin jump” (they will love it).
Constructing the Rotating “Paper Protractor”
Students begin making their adjustable paper protractor by coloring their 30 degree sheet (page 119) with a single color crayon. Then they follow three steps to cut it out. First, they cut around the circle. Second, they cut down the dotted line leading to the middle. Finally, they carefully cut out the very small black dot in the circle’s center.
1 Normally, students use their “Paper Protractors” when creating their “Angle Comparison Strips.” However, teachers of older students might pass over the “Paper Protractor” project, choosing instead to have students construct the “Angle Comparison Strip” using regular protractors.