1. 8-4 Properties of Circles Do Now
Course 2
8-4
Properties of Circles
Do Now
1. Two angles are supplementary. One angle measures 61°. Find the measure of the other angle.
2. Two angles are complementary. One angle measures 19°. Find the measure of the other angle.
3. Two angles are supplementary and congruent. Find the measure of each angle.
119°
71°
90°
Hwk: p 71

2. 8-4 Properties of Circles Problem of the Day
Course 2
8-4
Properties of Circles
Problem of the Day
In a circle graph, three sectors representing 15%, 25%, and 30% are labeled. What percent does the fourth sector represent, and what is its measure in degrees?
30%; 108°

3. 8-4 Properties of Circles
Course 2
8-4
Properties of Circles
EQ: How do I identify parts of a circle and to find central angle measure?
M7P3.d Use the language of mathematics
to express mathematical ideas.

4. Insert Lesson Title Here
Course 2
8-4
Properties of Circles
Insert Lesson Title Here
Vocabulary
circle
center of a circle
radius
diameter
chord
arc
central angle
sector

5. 8-4 Properties of Circles
Course 2
8-4
Properties of Circles
A circle is the set of all points in a plane that are the same distance from a given point, called the center of a circle.
A circle is named by its center. For example, if point A is the center of a circle, then the name of the circle is circle A. There are special names for the different parts of a circle.

6. 8-4 Properties of Circles Diameter Arc
Course 2
8-4
Properties of Circles
Diameter
Arc
Part of a circle named by its endpoints
Line segment that passes
through the center of a circle, and whose endpoints lie on the circle
Radius
Line segment whose endpoints are the center
of a circle and any point on the circle
Chord
Line segment whose
endpoints are any two
points on a circle

7. 8-4 Properties of Circles Name the parts of circle M. A. radii:
Course 2
8-4
Properties of Circles
Name the parts of circle M.
A. radii:
MN, MR, MQ, MO
B. diameters:
NR, QO N
C. chords:
D. Arcs:
NR, QO, QN, NP O P M Q R
Radii is the plural form of radius.

8. 8-4 Properties of Circles Name the parts of circle M. A. radii:
Course 2
8-4
Properties of Circles
Name the parts of circle M.
A. radii:
GB, GA, GF, GD B
B. diameters:
BF, AD A C
C. chords:
D. Arcs:
AH, AB, CE,
BF, AD G D H F E

9. 8-4 Properties of Circles A central angle of a circle
Course 2
8-4
Properties of Circles
Sector
A central angle of a circle
is an angle formed by two
radii. A sector of a circle
is the part of the circle
enclosed by two radii and an
arc connecting them. )
The sum of the measures of all
of the central angles in a circle
is 360°. We say that there are
360° in a circle.
Central angle

10. 8-4 Properties of Circles
Course 2
8-4
Properties of Circles
The circle graph shows the results of a survey about favorite types of muffins. Find the central angle measure of the sector that shows the percent of people whose favorite type of muffin is blueberry.

11. 8-4 Properties of Circles
Course 2
8-4
Properties of Circles
The circle graph shows the results of a survey about the favorite types of muffins. Find the central angle measure of the sector that shows the percent of people whose favorite type of muffin is banana nut.

12. 8-4 Properties of Circles
Course 2
8-4
Properties of Circles
The circle graph shows the results of a survey about the favorite types of muffins. Find the central angle measure of the sector that shows the percent of people whose favorite type of muffin is bran.

13. 8-4 Properties of Circles
Course 2
8-4
Properties of Circles
The circle graph shows the results of a survey about the favorite types of muffins. Find the central angle measure of the sector that shows the percent of people whose favorite type of muffin is other.

14. Properties of Circles Quiz Insert Lesson Title Here
Course 2
8-4
Properties of Circles Quiz
Insert Lesson Title Here
Name the parts of circle B.
1. radii
2. diameter(s)
3. chord(s) 4.
BA, BC AC
DE, FE, AC
A pie is cut into 8 equal sectors. Find the
measure of the central angle of one slice of
pie.
45°