Lesson 9

The purpose of this lesson is for students to understand \(1^\circ\) as a measurement of a turn through \(\frac{1}{360}\) of a circle and to use a protractor to measure angles.

Before this lesson, students have compared and measured angles using informal tools (analog clocks) and reference angles, all of which were multiples of \(5^\circ\) or multiples of \(10^\circ\). In this lesson, students transition to measuring angles in units of \(1^\circ\).

Students then make sense of one-degree angles in terms of a fraction of a \(360^\circ\) turn and are introduced to the protractor as a tool of measurement. They make sense of the numbers on the tool and how \(1^\circ\) angles are shown. They learn to read the measurement of angles whose vertices have been pre-aligned to the center point of a protractor.

Students will continue to add new vocabulary to their personal word walls. In the next lesson, students will further develop their ability to use a protractor by measuring a variety of angles with less support.

The first two activities offered opportunities for students to take multiple solution paths. Were all unique perspectives or strategies heard? Which students were able to share their ideas? Which didn’t get a chance? How can their voices be added into the conversation tomorrow?