Lesson 8 The Size of Angles in Degrees

    • Let’s describe the size of angles using degrees.

Warm-up What Do You Know About …?

What do you know about 360?

Activity 1 A Full Turn

Problem 1

A ray that turns all the way around its endpoint and back to its starting place has made a full turn.

We say that the ray has turned 360 degrees.

ray moving around a point. 360 degrees

How many degrees has the ray turned from where it started?

  1. ray moving around a point. 360 degrees

Problem 2

Sketch two angles:

  1. an angle where a ray has turned

  2. an angle where a ray has turned

Activity 2 Make a Measuring Tool

Your teacher will give you a sheet of paper in the shape of half a circle. It shows a angle and a angle from the ray on the bottom right.

image of a half circle.

On the half-a-circle paper:

  1. Draw a line segment to show a angle from the same ray. Label it with the measurement. Be as precise as possible.

  2. Draw lines to show the following angles (measured from the same ray). Label each line with the measurement.

  3. Can you find a angle from that same ray? Explain or show how you might do it.

  4. You just made a measuring tool!

    How can it be used to estimate the size of an angle? Discuss your ideas with your group. Then, use your tool to estimate the sizes of at least two angles.

    image of 4 different angles

Practice Problem

Problem 1

This angle has a measure of .

angle formed by two rays
  1. How many of these angles can you put together, without overlaps, to make a complete circle? Explain or show how you know.

  2. Explain how you can use the given angle to sketch a angle.