1. Circles

2. Segments
of Circles

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

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

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

6. Distance across the circle through its center
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. Use P to determine whether each statement is true or false.Q R T S
True: thumbs up False: thumbs down

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

10. a LINE that intersects the circle exactly ONE time
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. Secant Radius Diameter Chord Tangent
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
Major Arc
Minor Arc
More than 180°
Less than 180°
ACB P AB
To name: use 3 letters C
To name: use 2 letters B
APB is a Central Angle

14. Semicircle: An Arc that equals 180°
To name: use 3 letters E D
EDF 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
96 Q
m AB =
96° B C
m ACB =
264°
m AE =
84°

17. Arc Addition PostulateB
m ABC =
+ m BC
m AB

18. 240 260 m DAB = m BCA = Tell me the measure of the following arcs. D
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