1. Circles Lesson 15.8

2. Vocabulary A circle is a plane figure that consists of a set of points that are equidistant from a given point called the center.

3. Identifying the Parts of a Circle A radius is a line segment that connects the outside of the circle to its center.

4. A diameter is a line segment with both endpoints on the circle that passes through the center.

5. A chord is a line segment whose endpoints are on the circle. Chords do not have to pass through the center of the circle. However, if a chord does pass through the center, it is also considered a diameter.

6. Numerical Relationships A radius is exactly one-half of a diameter. Therefore a diameter is twice a radius. 5.5 cm If the radius is 5.5 cm, then the diameter is ___________ cm. 11

7. A central angle is an angle with its vertex at the center of the circle.

8. Practice Time