6th Grade Math Textbook, Progress

Circles

10-12

Use the circle for exercises 1–9.

The length of the diameter (d) is

twice the length of the radius (r).

d
 2 r r
d 2

1. What is the center of the circle?


2. What is IJ
   called?


3. Name two diameters of the circle.


4. Name all the radii shown in the circle.


5. What is the curved part of the circle
   that joins point Gand point Fcalled?


6. Name all the semicircles shown.
   5. Name two central angles of the circle.
   7. Name two minor arcs and two major arcs.
   9. What is the region bounded by K
   A
   ,
   KL, and L
   A
   called?

A circle is a set of points in a plane, all of which

are the same distance from a given point, called

the center. A circle is named by its center.

Point Pis the center of circle P.

A radius (plural:radii) is a line segment from the

center of a circle to a point on the circle. PK
, PL
,

and PA
are radii of circle P.

A central angle has its vertex at the center of the

circle. 
APCand 
IPLare central angles of circle P.

A chord is a line segment with its endpoints on

the circle. AC
is a chord.

A diameter is a chord that passes through the

center of a circle. CI
and AG
are diameters.

An arc is a part of a circle, with all of its points on the circle. An arc that connects

the endpoints of a diameter has a measure of 180° and is a semicircle. A

minor arc is an arc with a measure less than 180°. A major arc is an arc with

a measure greater than 180°. ABis an arc of circle P.

ACGis a semicircle. ABCis a minor arc. CKE is a major arc.

m ACG
180° mABC180° mCKE 180°

A sector of a circle is the region bounded by two radii and their intercepted arc.

The shaded region is a sector of circle P.

A G

K I

L

P

C E

B

F

H L

K

A

J

I

G

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