The document explains the concepts of a circle, including the definitions of the center, radius, diameter, and circumference. It provides relationships between these elements, such as the radius being half the diameter and the approximation of the circumference being three times the diameter. Additionally, it includes example problems to illustrate these relationships.

1. The Circle

2. O A
CIRCLE
Eg. ball,bangle,lemon.coin

3. O
A
CENTRE : O
RADIUS : OA
B
CENTRE
RADIUS

4. .
O
In a plane,each point of the circle is at equal
distance from a fixed point.The fixed point is
called the centre of the circle.
CENTRE = O

5. O
The distance from centre to any point on the
circle is called radius of the circle.
A
RADIUS = OA
Radius

6. .
O
DI
A
M
E
T
E
R
A Line segment passing through the centre of
the circle and whose end points lie on the circle
is called the diameter of the circle.
A
B
DIAMETER = AB

7. .
O
The length of the circle or the distance
around it is called circumference of the
circle.

8. .
O
A B
A Line segment whose both the ends touches
the circumference and passes through the
centre is called diameter.
DIAMETER : AB

9. Relation between radius and diameter
.
O
A B
RADIUS = DIAMETER
2
OB = AB
2

10. Eg. If diameter of the circle is 10 cm then find
its radius?
.
O
Diameter = 10cm
Sol. Radius =diameter / 2
radius=10 cm/ 2
radius =5 cm
A B

11. .O
Eg. If radius of the circle is 6 cm,then find the
diameter of the circle?
Radius = 6cm
A
Sol. Diameter = 2 x Radius
Diameter = 2 x 6cm
Diameter = 12 cm

12. RELATION BETWEEN CIRCUMFERENCE AND
DIAMETER
.
O
DIAMETER
CIRCUMFERENCE = 3 x DIAMETER(APPROX)
A B

13. Eg. Find the circumference (approx) of the circle whose
diameter is 10cm.
.
O
DIAMETER=10 CM
Sol. Circumference = 3 x
diameter(approx)
Circumference = 3 x 10 cm
Circumference = 30 cm
A B

14. EVALUATION
1. what is the relation between radius and diameter of the
circle?
.
O
A B
2. What is the relation between circumference and diameter
of the circle?
3. In this figure
Sol .Radius=diameter/2
Sol. Circumference=3Xdiameter(approx)
radius
diameter
centre
AB is ________.
O is _________.
OA or OB is ______.

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