1. Types of Angles

2. Angles form when rays share the same endpoint. This common endpoint is called the vertex. The two sides are rays of the angle. ray vertex

3. A Matter of Degrees Angles are measured in degrees. There are 90 degrees (90°) in a square corner like the one shown here.

4. Right Angles You will learn about four different types of angles. The first is a right angle. Right angles measure exactly 90°. The angles at the corners of this rectangle are right angles.

5. Acute Angles Angles that have a measure between 0° and 90° are called acute angles. The angles at the corners of a yield sign are acute angles. They are smaller than right angles.

6. Obtuse Angles Obtuse angles are big. They measure between 90° and 180° The angles formed on the corners of a stop sign are all obtuse angles.

7. Straight Angles Straight angles have a measurement of exactly 180°. A straight angle looks like this:

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