1. Unit Question: What are the properties and characteristics of circles? Today’s Question: How does the measure of an arc compare to the measure of its central angle?

3. 11.1 Parts of a Circle Circle – set of all points _________ from a given point called the _____ of the circle. C Symbol: equidistant center C

4. 11.1 Parts of a Circle P RADIUS= distance from the _____ to a point on the circle center

5. CHORD: a segment whose ________ are on the circle endpoints

6. Diameter P DIAMETER: distance ______ the circle through its ______ center across Also known as the longest chord.

7. What is the relationship between the diameter and the radius of a circle? r = OR D = ½ D 2 r

8. D = ? r = ? D = ?

9. Use  P to determine whether each statement is true or false. P Q R T S

10. Same center but different radii

11. P Q R T S Ex. 4 14

12. P Q R T S Ex. 5 18

14. P A B C Central Angle : An Angle whose vertex is at the center of the circle Minor Arc Major Arc Less than 180° More than 180° AB ACB To name: use 2 letters To name: use 3 letters <APB is a Central Angle

15. P E F D Semicircle: An Arc that equals 180° EDF To name: use 3 letters

16. Measure of an arc is equal to the measure of the central angle

17. THINGS TO KNOW AND REMEMBER ALWAYS A circle has 360 degrees A semicircle has 180 degrees Vertical Angles are Equal

18. Find the measure of an the following arcs. EB is a diameter. A B C Q 96  m AB m ACB m AE E = = = 96  264  84 

19. Arc Addition Postulate A B C m ABC = m AB + m BC

20. Tell me the measure of the following arcs. 80  100  40  140  A B C D R m DAB = m BCA = 240  260 