# Finding Measurement of Angles: 4th Grade Lesson

Students will investigate the concept of angles and determine the measurement of angles using a cut-out of a one-degree of a circle.

Identify a “one-degree angle” as an angle that turns through 1/360 of a circle. This angle can be used to determine the measurement of angles. Go to the bottom of the article to download a copy of the lesson.

**Lesson Objective:** The lesson is aligned to the Common Core State Standards for Mathematics – 4MD.5a and b Geometric Measurement – Recognize angles as geometric shapes that are formed wherever two rays share a common endpoint.

**Materials Required: **Cutout of one-degree angle

## Lesson Procedure:

**Identifying Measurement of an Angle using a “One-Degree Angle”**

Look at the circle below. Point *O* is the center of the circle. Both Ray *a* and Ray *b* share a common endpoint, Point *O*. Ray *a* and Ray *b* form an angle. Ray *a* and Ray *b* are the sides of the angle. The angle on the circle turns through 1/360 of the circle. This angle is called a “one-degree angle”.** **This angle measures one degree.

**Student Work**

Cutout the “one-degree angle” above. Use the “one-degree angle” to draw angles with the following measurements.

- On your paper, draw an angle that measures 3 degrees.
- On your paper, draw an angle that measures 5 degrees.
- On your paper, draw an angle that measures 8 degrees.
- On your paper, draw an angle that measures 10 degrees.

## Individual or Group Work:

Use the “one-degree angle” that you cutout from the activity above to draw angles with the following measurements.

- On your paper, draw a circle. Label the center of the circle with Point
*O*. Draw Ray*a*and Ray*b*to form an angle with endpoints at the center of the circle and measures 2 degrees. - On your paper, draw a circle. Label the center of the circle with Point
*O*. Draw Ray*f*and Ray*g*to form an angle with endpoints at the center of the circle and measures 4 degrees. - On your paper, draw a circle. Label the center of the circle with Point
*O*. Draw Ray*m*and Ray*n*to form an angle with endpoints at the center of the circle and measures 7 degrees. - On your paper, draw a circle. Label the center of the circle with Point
*O*. Draw Ray*p*and Ray*q*to form an angle with endpoints at the center of the circle and measures 9 degrees.

Answer the following two questions for each of the shaded angles shown below.

- How many “one-degree angles” did you use to measure each of the shaded angles?
- How many degrees do the shaded angles measure?

**Answers:**

- Students should trace around the “one-degree angle” three times to draw an angle that measures approximately 2 degrees.
- Students should trace around the “one-degree angle” five times to draw an angle that measures approximately 4 degrees.
- Students should trace around the “one-degree angle” eight times to draw an angle that measures approximately 7 degrees.
- Students should trace around the “one-degree angle” ten times to draw an angle that measures approximately 9 degrees.
- 14 “one-degree angles”, 14 degrees
- 28 “one-degree angles”, 28 degrees

Students should be able to draw and measure angles with a specified measurement using a model of a “one-degree angle”.