Transcript Circles

Circles
Parts of a Circle
Area & Circumference
PARTS OF A CIRCLE
Circumference
The
circumference
of a circle is
the distance
around the
outside of a
circle
Diameter
The diameter of the circle is the distance from
one side to the other passing through the
centre of the circle
Chord
A chord is a line touching the
circumference of the circle at two
points
Radius
The radius is the line connecting the
centre of the circle and the circumference
A segment is the part of a circle between a
chord and an arc
Segment
A tangent
is a
straight
line which
touches a
circle at
one point
only
Tangent
CIRCUMFERENCE OF A CIRCLE


Formula is C = 2r (2 x Pi x Radius)
or
C = d (Pi x Diameter)
Remember… = 3.14 (approximately)
The circumference of a circle
Use π = 3.14 to find the circumference of this circle.
C = πd
8 cm
= 3.14 × 8
= 25.12 cm
The circumference of a circle
Use π = 3.14 to find the circumference of the following circles:
4 cm
C = πd
C = 2πr
= 3.14 × 4
= 2 × 3.14 × 9
= 12.56 cm
= 56.52 m
C = πd
23 mm
9m
58 cm
C = 2πr
= 3.14 × 23
= 2 × 3.14 × 58
= 72.22 mm
= 364.24 cm
AREA OF A CIRCLE

Formula is A = r2
(Pi x Radius Squared)
radius
Area of a circle = πr2
The circumference of a circle
Use π = 3.14 to find the area of this circle.
4 cm
A = πr2
= 3.14 × 4 × 4
= 50.24 cm2
The area of a circle
Use π = 3.14 to find the area of the following circles:
2 cm
A = πr2
= 3.14 ×
A = πr2
22
10 m
= 12.56 cm2
A = πr2
23 mm
= 3.14 × 52
= 78.5 m2
78 cm
A = πr2
= 3.14 × 232
= 3.14 × 392
= 1661.06 mm2
= 4775.94 cm2