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Math for Kids23 chapters | 325 lessons

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Instructor:
*Lisa Hanson*

Lisa is a Continuous Improvement Coach for her school district and has taught in elementary school for many years. She has a master's degree in curriculum and instruction.

Get ready to wrangle up some angles! We can find angles everywhere. In this lesson, you will learn about types of angles and how to measure them with a protractor.

There are angles all around us! We see them in shapes, on furniture, walls, floors, and even on playgrounds.

An **angle** is formed by two rays connected by a point, or **vertex**.

When we want to measure an angle, we measure the space between the two rays. This is measured in degrees. These are not the same kind of degrees you hear about when the weather is cold or hot. We use a special tool called a **protractor** to measure angles.

A right angle has a measurement of 90 degrees, which is written 90°. This means that one side is perfectly flat, or horizontal, and the other is going straight up and down, or vertical. You can see an example in the picture below. You see this type of angle all over the place, especially on things that are rectangular or square in shape. We compare all angles to a right angle to see if the space between the rays is bigger or smaller than 90°.

The space between the two sides of an acute angle is always less than the right angle. This means that an acute angle is less than 90°. It can measure anywhere from 0-89°. You can see an example in the picture. If you look at a triangle, at least two of the corners are always acute angles. A way to remember the name is to think of an acute angle as a 'cute' angle because it is smaller.

The space between the two sides of an obtuse angle is always bigger than the right angle. So, an obtuse angle is larger than 90°. It can measure anywhere from 91-179°. See the picture below for an example. The obtuse angle is thought to be a 'fat' angle.

If you follow these five easy steps, you should be able to measure any angle. Protractors are always made clear so that you can place them right on top of your angles.

1. Look at your angle and ask yourself, 'Is this a right, acute, or obtuse angle?' This will help you know if it is greater than, equal to, or less than 90 degrees.

2. Place the center hole of the protractor over the vertex of your angle.

3. Rotate the protractor so that the straight edge lines up with one side of the angle.

4. Locate the spot where the second side of the angle crosses with the numbers on the protractor.

5. Read the number where the line crosses on the protractor to find the angle measurement.

**Angles** are two rays connected by a **vertex**. We use a **protractor** to measure the degrees of an angle. Angles can be called right (90°), acute (less than 90°), or obtuse angles (more than 90°) depending on their angle measurements.

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Math for Kids23 chapters | 325 lessons

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