Circles

1. Circles

2. Segments of Circles

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

4. CHORD: A segment whose endpoints are on the circle

5. Radius RADIUS: Distance from the center to point on circle P

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

7. D = ? 24 32 12 r = ? 16 r = ? 4.5 6 D = ? 12 9

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

9. Secant Line: intersects the circle at exactly TWO points

10. Tangent Line: a LINE that intersects the circle exactly ONE time Forms a 90°angle with a radius Point of Tangency: The point where the tangent intersects the circle

11. Name the term that best describes the notation. Secant Radius Diameter Chord Tangent

12. Central Section 6.2 Arcs

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

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

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

16. measure of an arc = measure of central angle m AB m ACB m AE A E 96 Q = 96° B C = 264° = 84°

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

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

19. CONGRUENT ARCS Congruent Arcs have the same measure and MUST come from the same circle or of congruent circles. C B D 45 45 110 A Arc length is proportional to “r”

20. Classwork • Practice Worksheet

21. Homework: • Practice Worksheet