1. Parts of a Circle
Circle – set of all points _________ from a given point called the _____ of the circle (in a plane).
equidistant C
center
Symbol: C

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

3. RADIUS: distance from the _____ to a point on the circle
center P

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

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

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

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

8. SECANT sounds like second
Secant Line
A secant line intersects the circle at exactly TWO points.
SECANT sounds like second

9. TANGENT: a LINE that intersects the circle exactly ONE time

10. Point of Tangency

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

12. Two circles can intersect…
in two points
one point
or no points

13. No points of intersection (different center)

14. No points of intersection (same center)
Concentric Circles
Same center but different radii

15. 1 point of intersection (Tangent Circles)
Externally Tangent
Internally Tangent

16. 2 points of intersection

17. A point is inside a circle if its distance from the center is less than the radius.
INTERIOR 

18. EXTERIOR 
A point is outside a circle if its distance from the center is greater than the radius.

19. A point is on a circle if its distance from the center is equal to the radius.

20. More Pythagorean Theorem type problems! Yeah!! 
Point of Tangency
More Pythagorean Theorem type problems! Yeah!! 
If a line (segment or ray) is tangent to a circle, then it is perpendicular to the radius drawn to the point of tangency.

21. 1. Find x A 12 B 9
a2 + b2 = c2 x
= x2
x = 15

22. RQ = 16 2. Find RQ a2 + b2 = c2 P 12 8 R Q 122 + (QR)2 = (8+12)2

23. r = 10 r2 + 242 = (r + 16)2 3. Find the radius. 16 A C 24 B

24. S
If two segments from the same exterior point are tangent to a circle, then they are congruent. R T
Party hat problems!

25. 4. Find x R S T

26. 5. Find x C A B

27. 6. Find x. B A C P D E

28. 7. Find NP N T S P R Q