*Contributor: Ashley Nail. Lesson ID: 13068*

"I Spy" angles all around us! In this lesson, you will learn the difference between right, acute, and obtuse angles. Then, you will play "acute" game to see if you can identify all the "right" angles!

categories

subject

Math

learning style

Visual

personality style

Otter, Beaver

Grade Level

Intermediate (3-5)

Lesson Type

Skill Sharpener

- Have you and your friends ever played I Spy?

It's a fun game you play where you take turns finding things in the world around you. Normally, you give hints to your friends, like “it's green,” “it's small,” or “it's round.”

For example, if I were on this playground and said, "I spy something round that is black and white,” I bet you could guess I was talking about the soccer ball!

- Well, did you know you can also play I Spy using geometry and angles?

Before you play, let's learn more about angles!

Look at the roof of the jungle gym from the playground. That is an example of an angle.

*Angles* are two rays that share a *vertex*. A *ray* is a line that starts at one point and then goes on forever.

On the roof of the jungle gym, the vertex is the pointy top. The two sides of the roof are like the rays that make up the angle. The two sides, or rays, share a vertex at the pointy top of the roof.

For example, look at the ray we will call YZ.

The ray starts at the dot labeled Y. That is the vertex. The ray continues on past the dot labeled Z. This is a ray named YZ. It is red.

When two rays share a vertex, they are, together, called an angle. Look at the new ray named YX. The new ray is blue.

Ray YX starts at the dot labeled Y. The ray continues on past the dot labeled X. Both rays share the same vertex, the dot labeled Y. These two rays together make an angle. This angle is called XYZ. It is green.

There are a lot of different types of angles. They are measured in *degrees*. The rays that make up angles can be close together or far apart. When the rays are close together, there are less degrees. When rays are farther apart, there are more degrees.

When the two rays of an angle are exactly up and down, they are called *right angles*. A right angle measures 90°. This type of angle makes a corner, like in a square or rectangle.

If the two rays of an angle are closer together, they will measure less than 90°. These are called *acute angles*. Look at the examples below.

If the two rays of an angle are far apart, they will measure more than 90°. These are called *obtuse angles*. Look at the examples below.

So, the three types of angles we will use in I Spy are called right angles, acute angles, and obtuse angles.

Now, practice spying the different types of angles on the playground! Click NEXT to go to the *Got It?* section.

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