3. BEHAVIORAL OBJECTIVES
The students will be able to :
1) define circle.
2) write the related terms of the circle.
3) give examples of circles.
4) construct circle with the help of circular objects.
5) establish relationship between radius & diameter and
chord & diameter, respectively.
6) take interest in demonstration of circle and its related
terms to the class.
7) review his/her knowledge for circle and its related
terms.
7. A circle can be drawn with the help of a circular object.
For example: A circle drawn with the help of a coin.
A circle is a closed curve in a plane.
8. This fixed point (equidistant)
inside a circle is called
centre.
A circle is a closed curve
consisting of all points
in a plane which are at the
same distance (equidistant)
from a fixed point inside it.
O
Centre
A circle
A circle has one and only
one centre.
9. The distance around a circle is called its circumference.
O
Centre
A circle
A
10. A circle divides a plane into three parts.
2. Interior of a circle
3. Exterior of a circle
A plane
O
Centre
The interior of a circle together with its circumference
is called the circular region.
1. The circle
11. A line segment that joins any point on the circle to its centre
is called a radius.
p
A point on the circle
Centre
O
(Contd…)
12. Radii ( plural of radius) of a circle are equal in length.
Infinite number of radius can be drawn in a circle.
Centre
K
O
L
M
N
(Contd…)
13. A line segment that joins any two points on the circle and
passes through its centre is called a diameter.
A
B
A circle
O Centre
(Contd…)
14. A circle
O
M
Infinite number of diameters can be drawn in a circle.
As the radii of a circle are equal in length, its diameters too
are equal in length.
B
D
(Contd…)
Centre
C
A
N
15. The length of the diameter of a circle is twice the length of its
radius.
Radius OC
Centre
C
O
D
Radius OD
Diameter CD
Diameter CD = Radius OC + Radius OD
Radius OC = Radius OD
(Contd…)
16. A line segment that joins any two points on the circle is
called a chord.
O
N
M
M is a point on the
circle
N is another point
on the circle
17. Diameter is also a chord of the circle.
O
Chord CD
C D
M
N
K
L
(Contd…)
Diameter CD
18. The diameter is the longest chord.
O
Diameter CD
C D
M N
Chord MN
(Contd…)
C D
M N
Chord KL
L
K
19. L
K
M N
Chord MN
O Centre
Infinite number of chords can be drawn in a circle.
G
H
20. O
Centre
An arc is the distance between any two points on the
circumference of a circle.
K L
(Contd…)
21. O
Centre
L
K
An arc is named by three points, of which two are the end
points of the arc and the third one lies in between them.
X
Naming an arc
(Contd…)
Arc KXL
22. O
Centre
L
K
X
Y
An arc divides the circle into two parts: the smaller arc is
called the minor arc, the larger one is called the major arc.
Minor Arc KXL
Major Arc KYL
(Contd…)
24. Half of a circle is called a semicircle.
Centre
O
Diameter
D E
S
A semicircle is also an arc of the circle.
R
Arc DSE
Semicircle DRE
(Contd…)
Semicircle DSE
Arc DRE
26. A chord divides the circular region into 2 parts, each of
which is called a segment of the circle.
Centre
O
D E
Chord DE
Minor segment of a circle
Major segment of a circle
S
R
(Contd…)
27. Centre
O
D E
Chord DE
Minor segment of
the circle
Major segment of the
circle
P
Q
Minor arc DPE
Major arc DQE
The part of the circular region enclosed by a minor arc and
the chord is called a minor segment.
Minor segment does not contain the centre of the circle.
The part of the circular region enclosed by a major arc and
the chord is called a major segment.
Major segment contains the centre of the circle.
33. Radius Diameter Chord Arc
Semi
circle
S
Centre
O
Diameter
Semicircle
D E
Semicircle DSE
Semicircle
34. 1. what is the relation between radius and diameter of the
circle?
.
O
A
2. What is the relation between chord and diameter of the
circle?
3. In this figure
Sol .Radius=diameter/2
Sol. Diameter is the longest chord.
Sol. Yes
Is the semicircle AB also an arc ?
B
