Angle Measurements

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SWBAT measure angles using a protractor and create angles to specifications; SWBAT classify angles and identify complementary and supplementary angle pairs.

Big Idea

Tool Time! In this lesson, students learn to use a protractor to measure and create angles.

Concept Development

10 minutes

This is the first time students are using protractors in my class. So the first order of business is demonstrating how to use the protractor. First I establish some vocabulary: initial side, vertex, and terminal side.

Then I show the steps:

1. Place the "sight" of the protractor at the vertex of the angle.

2. Zero the protractor on the initial side of the angle.

3. Determine the intersection of the terminal side with the protractor's measurement scale (noting that sometimes it's necessary to extend the terminal side).

Students often ask about whether they should use the upper or lower numbers on the protractor. I answer this two ways:

1. Remember that starting from the initial side of the angle (which is determined by the measurer) you should start at zero, not 180, on the measurement scale.

2. You should know intuitively whether the angle you're measuring is acute or obtuse, so choose the reasonable one.

After this basic refresher on protractors, it's time for students to get some hands on experience.


Hands On Training

20 minutes

For this section, I hand each student a protractor and the Measuring Angles resource. Students work on this independently with help from their neighbors as needed.

I walk around making sure that students are using proper notation, e.g. m∠PST=20 degrees and not just "20".

I also make sure that students are being precise with their measurements. If a student has been imprecise, I say "Show me how you measured angle ABC the angle measure exactly 140 degrees, or can we be more precise?"

On the back side of the handout, I go around with my protractor measuring students angles to make sure that they have been precise. And on the last two problems, I am making sure that students have not neglected the non-congruent constraint.

Cooperative Activity: Measuring Range of Motion

40 minutes

In this section, I introduce some basic anatomy concepts related to range of motion. This section gives students an opportunity to see some real-life applications of angle measures in a fun, relaxed atmosphere.

I start with some physical exercises that demonstrate the different types of joint movement. 


Flexion/Extension: I model extending my forearm, then flexing it. Then I have student do it. To check for understanding, I ask the students to show me neck neck flexion.


Rotation: I demonstrate neck rotation. Then I ask students, "Are there any other joints in your body that you can rotate?"


Abduction/Adduction: I demonstrate arm abduction (toward the midline) and arm adduction (away from the midline), then ask student to demonstrate leg adduction and leg abduction.

I also show students an online animation that demonstrates these anatomical movements.


Time permitting, we might also do some basic 'Simon Says' with anatomical movements..."Simon says demonstrate hip flexion" and so forth.


Finally I introduce the concept of range of motion, using neck extension/flexion as an example. I explain that it's an important way for physical therapists and doctors, for example, to measure joint health.

Then organize students into groups of three and give each group the Cooperative Activity_Measuring ROM. I'm not prescriptive when it comes to the methods students use to measure joint angles. I want them to be creative. It's not the accuracy that is of primary importance in this exercise, but rather the awareness of the angles they are attempting to measure.

Reflection and Discussion

15 minutes

Each student writes a reflection on what they learned in the lesson and discusses the methods they used to measure range of motion.