Geometry 11-3 Areas of Circles and Sectors
The area of a circle is found by multiplying the square of the
radius by pi.
radius
A = r2
An archery target has a diameter of 24 inches. What is the
area of the target?
d = 24 in
r = 12 in
A = (12)2 = 452.389 in2
The area of a circle is 196 yd2. Find the radius.
196 = r2
r = 14 yd
A sector
of a circle is a portion of the circle bounded
by a central angle and its intercepted arc.
sector
As we did with arc length, we will use a proportion to find the
area of a sector.
Sector Angle
A
x
=
=
r2 360
Circle
360
Find the area of the shaded sector.
148 6 m
A 148
=
(6)2 360
360A = 148 (6)2
A = 46.496 m2
11 in 65
360 - 65 = 295
A 295
=
(11)2 360
360A = 295 (11)2
A = 311.498 in2