Naming Circles

1. Naming Circles Section 10.1

2. A circle is the set of all points in a plane at a given distance from a given point in the plane. • The given point is the center of the circle. • You name a circle by its center. • The given distance is the radius. • A radius is a segment from the center of a circle to any point on the circle.

3. Name Center O L Radius

4. Like all other plane figures, a circle divides a plane into three regions: the interior of the circle, the exterior of the circle, and the circle itself.

5. Other parts of a circle • A chord is a segment that connects any two points on a circle. It does not have to go through the center.

6. A diameter is a chord that goes through the center of a circle.

7. A secant is a line that contains a chord. Basically it is a line that goes through any two points on a circle.

8. A tangent to a circle is a line that passes through only one point on the circle called the point of tangency.

9. An arc consists of two points on the circle and the continuous (unbroken) part of the circle between the two points. • The two points are called the endpoints of the arc.

10. Types of Arcs • A semicircle is an arc of a circle whose endpoints are the endpoints of a diameter. • A minor arc is an arc of a circle that is less than a semicircle of the circle. • A major arc is an arc of a circle that is greater than a semicircle of the circle.

11. Semicircle Minor Arc Major Arc

12. Naming Arcs • You name a minor arc using the two endpoints. • You name a semicircle and a major arc with three letters. You use the two endpoints and a point in between. C B A B A

13. More parts of a circle • A centralangle of a circle is an angle with its vertex at the center of the circle. • An inscribed angle is an angle whose vertex is on a circle and whose sides contain chords of the circle. • The part of a circle between the two sides of a central angle or an inscribed angle is called the intercepted arc.

14. Central Angles Inscribed Angles