6th Grade Math Textbook, Fundamentals

L

R

M

N

Q S

70

LNMis a central angle.

m mLNM 70

mLQM 360 

mLRM 360 

 70 

 290

LRM

 &KDSWHU

9-12

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

The shaded region is a sector of circle P.

The arc from car 7 to car 25’s location is a semicircle. It has a measure

of 180. Car 23 comes before car 25, so the measure of the arc from car 7

to car 23 is lessthan 180. It is a minor arc.

The chords and radii of a circle form different kinds of angles.

A has its vertex at the center of a circle.

• The sum of the measures of all the nonoverlapping
  central angles of a circle is 360.


• The degree measure of a minor arc is the measure
  of its central angle.


• The degree measure of a major arc is 360
  minus the degree measure of the minor arc
  that completes the circle.

central angle

sector

Circles

Objective To identify parts of a circle• To name different kinds of arcs• To identify and

find the measure of central angles and inscribed angles• To identify secants and tangents

• To identify concentric, inscribed, and circumscribed circles

The first Ferris wheel had 36 cars. Suppose the cars
of a Ferris wheel are numbered from 1 to 36. You are
in car 7 and your friend is in car 23. If the wheel turns
in a clockwise direction, what kind of arc will be
made by your car as it moves from its current
location to car 23’s current location?

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

are the same distance from a given point called

the. A circle is named by its center.

A is a line segment with its endpoints

on the circle.

A (plural: radii) is a line segment from

the center of a circle to a point on the circle.

A is a chord that passes through the

center of a circle. It is twice the length of a

radius of that circle.

An is a part of a circle with all its points on

the circle. The symbol for arc ABCis.

There are three kinds of arcs:

center

ABC

arc

diameter

radius

chord

circle

A connects the

endpoints of a diameter.

It is a half circle.

mABC 180

semicircle A has a

measure lessthan 180.

mAED 180

minor arc A has a

measure greaterthan 180.

mBAC 180

major arc

1

5

9

13

17

21

25

29

33

A

B

C

E D

P

This is circle P. PA, PB, PC, and PD

are radii of circleP. ACandBDare

diameters. AB, AC, and BDare chords.