Geometry Notes G.11 Circumference/Area of Circles and Sectors
Mrs. Grieser
Name: ________________________________________ Date: _______________ Block: _______
Circumference and Arc Length


Circumference: distance around the circle
Arc Length: portion of the circumference
Circumference of a circle = C   d  2 r
Arc Length Corollary
In a circle, the ratio of the length of a given arc to the circumference is equal
to the ratio of the measure of the arc to 360o.
Examples:
a) Find the circumference of a circle with radius
9
Exact Answer:
Estimated Answer:
b) Find the radius of a circle with circumference
26
Exact Answer:
Estimated Answer:
(leave in terms of π!)
c) Find the length of
(exact and estimated):
d) Find
(use
formula to solve for arc
measure)
You try (where possible, give exact and estimated answers)…
a) Find the circumference:
b) Find the
radius:
c) Find the
length of
:
d) Find the circumference:
e) Find the radius:
f)
A skateboard wheel has a
diameter of 56 mm. How
many revolutions does the
wheel make when traveling
3 meters?
Geometry Notes G.11 Circumference/Area of Circles and Sectors
Mrs. Grieser Page 2
Area of Circles and Sectors
Area of a circle = A   r 2

Sector of a Circle The region bounded by two radii of the circle and their intercepted
arc.
Area of a Sector
The ratio of the area of a sector of a circle to the area of the whole circle (πr2)
is equal to the ratio of the measure of the intercepted arc to 360o.
Examples:
a) Find the area of a circle with radius 2.5 cm
Exact:
Estimated:
b) Find the diameter of a circle with
area = 113.1 cm2
c) Find the areas of the
sectors formed by UTV
d) Find the area of
circle V
You try,,,
a) Find the area
b) Find the radius
c) Find the area of a circle with
diameter 11 cm.
d) Find the radius of a circle
with area 158.3 yd2.
e) Find the diameter of a circle
with area 1024π m.
f)
Find the area
of the sectors
formed by
PQR
g) Find the area of
Y.
h) Find the
areas of
the sectors
formed by
ABC
i)
Find the area of
H