Parts if a circle Circle-Introduction.ppt

The learner derives inductively the relations
among chords, arcs, central angles, and
inscribed angles. (M10GE-IIc-1)
Learning Objectives:
a. identify the chords, arcs, central angles
and inscribed angles of a circle;
b. name the chords, arcs, central angles, and
inscribed angles of a circle; and
c. show cooperation while doing the assigned
task.
.
Learning Competency
10th
Grade

Motivational Activity:
4 Pics – One Word
Directions: Guess the missing word using the pictures at the
right:
c
c I
I L
L
C
C E
E
R
R

Parts of a Circle
Aim: To understand and know
the vocabulary for parts of a
circle.

Vocabulary
Circle
center of a circle
Radius
Diameter
Chord
Arc
Semicircle
central angle
inscribe angle

Use the figure below
to identify and name
the
following terms
related to O:
ʘ
1. a radius
2. a diameter
3. a chord
4. a semicircle
5. a minor arc
6. a major arc
7. 2 central angles
8. 2 inscribed angles

1. How did you find the activity?
2. How did you identify the radius,
diameter, and chord of a circle?
3. What is the difference between the
three lines?
4. How did you identify the minor
and major arcs of the circle?
5. How did you name chords, arcs
and angles of a circle?

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. This distance
is called the radius of the 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.
How do we name a circle? Ps/nv x2

B
A
What is the name of this circle?
How do you know?
WB
Ps/nv x2

Arc
Part of a circle named
by its endpoints
Radius
Line segment
whose endpoints
are the center
of a circle and any
point on the circle
Diameter
Line segment that
passes
through the center
of a circle, and
whose endpoints lie
on the circle
Chord
Line segment whose
endpoints are any two
points on a circle

What color is the…
Radius?
Diameter?
Arc?
Chord?
How did you know? Ps/nv x2
wb

)
Central angle
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.
What is the sum of all central angles in a circle?
PS/WB

Circumference
Diameter
The
circumference
of a circle is
the distance
around the
outside of a
circle
The diameter of the circle is the distance from
one side to the other passing through the
centre of the circle

Radius
Chord
A chord is a line touching the
circumference of the circle at two
points
The radius is the line connecting the
centre of the circle and the circumference

Sector
Arc
A sector is
the part of
a circle
between
two radii
and an arc
An arc is the part of the circumference
at the edge of a sector

Segment
Tangent
A segment is the part of a circle between a
chord and an arc
A tangent
is a
straight
line which
touches a
circle at
one point
only

Radius Diameter Sector Segment
Tangent Arc Circumference Chord
Copy the two diagrams carefully into your book
Label your two diagrams using the words below

Name the parts
of circle M.
1. Identify what you are looking for.
2. Name your starting point.
3. Name your ending point.
O
N
P
Q
R
M
A. radii:
B. diameters:
C. chords:
MN, MR, MQ, MO
NR, QO
NR, QO, QN, NP
Radii is the plural form of radius.
Reading Math
How did I/we name the radii? ps
How did I/we name the diameter?
How did I/we know ___ was a chord?

APPLICATION
Name the parts of circle B.
1. radii
2. diameter(s)
3. chord(s)
4. semicircle
BA, BC
AC
DE, FE, AC

Name the parts of circle M.
A. radii:
B. diameters:
C. chords:
A
B
C
D
E
F
G
H
D. semicircle:

Name the parts of circle M.
A. radii:
B. diameters:
C. chords:
GB, GA, GF, GD
BF, AD
A
B
C
D
E
F
G
H
AH, AB, CE,
BF, AD
D. semicircle:

Diameter Circumference
Chord Radius
Sector
Arc
Segment
_______1. The part of a circle between two radii and an arc
______2. The part of a circle between a chord and an arc
______3. The distance around the outside of a circle
______4. The distance from one side to the other passing through the
______5. A line touching the circumference of the circle at two points
_______6. The line connecting the centre of the circle and the
circumference
_______7. Part of the circumference at the edge of a sector
Match up the word with the correct definition.

Diameter
Circumference
The distance
around the
outside of a
circle
The distance from one
side to the other
passing through the
Chord
Radius
Sector
Arc
Part of the
circumference at the
edge of a sector
Segment
The part of a
circle between
two radii and an
arc
The part of a circle
between a chord and
an arc
The line connecting the
centre of the circle and
the circumference
A line touching the
circumference of the circle
at two points
Match up the word with the correct definition.

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 banana
nut.
How did we find the measure of the central angle? ps/nv
Why did we multiply by 360o
? Ps/ nv
1. Read the problem
2. Identify the percentage of the sector
3. Change the percent to a decimal
4. Multiply the decimal by 360o

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.
How did I find the measure of the central angle? Ps/nv
Why did I multiply by 360o
? Ps/ nv
1. Read the problem
2. Identify the percentage of the sector
3. Change the percent to a decimal
4. Multiply the decimal by 360o

Why is it important to know about parts of a
circle?
It will help you read and interpret circle
graphs?
You will need to know about the parts
of a circle in Algebra and Geometry.
It will be tested.
Why is it important to know about the parts of
a circle? Tell your partner. You can use one of
my reasons or use one of your own.
ps/volunteers

Independent Practice:
HOLT chapter 9 lesson 3

Extension Problems
Draw a circle with radius 4cm.
 What is the length of the diameter of the circle?
 How many sectors of 90° will fit inside the circle?
 Draw five radii inside your circle that are equally spaced out
around the circumference. Join up the ends of the radii to
create a shape inside your circle.
 What is the name of the shape that you have created inside
your circle?
 How long are the chords that are joining the radii together?
 How big is the angle of each sector?
 If you did the same as above with sectors of 45°, what shape
would you create inside your circle?

Parts if a circle Circle-Introduction.ppt

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