The document contains notes from a math class on the topics of area of circles, sectors, segments and annuli. It includes formulas for calculating these areas, examples of applying the formulas with given values, and practice problems for students to work through. Diagrams illustrate regions such as sectors and segments. The notes provide instruction on key concepts and calculations for finding areas of various parts of circles.

1. 11.5 Area of Circles & Sectors
HW pg. 758 #3­31 odds 1
March 31, 2014
Bellwork
about 56.5 cm.
8.64 cm
100.53 cm
7.64 ft

2. 11.5 Area of Circles & Sectors
HW pg. 758 #3­31 odds 2
March 31, 2014
A circle has an area of ≈ 38.485 in2
.
What is the circumference of the circle?
11.5 Areas of Circles & Sectors
Area of Circle = πr2
(fuzzy wuzzy)
4.2 m

3. 11.5 Area of Circles & Sectors
HW pg. 758 #3­31 odds 3
March 31, 2014
20 in
Find the area of the shaded region.
10 cm

4. 11.5 Area of Circles & Sectors
HW pg. 758 #3­31 odds 4
March 31, 2014
Sector of a Circle:
region bounded by 2 radii of a circle & the included arc
Formula for the Area of a Sector:
“portion of the circle times the area of the circle”
Asector =
x
360
πr2
r = 3 cm
120
o
r = 6cm
60
o

5. 11.5 Area of Circles & Sectors
HW pg. 758 #3­31 odds 5
March 31, 2014
Segment of a Circle:
region bounded by a chord of a circle
& the included arc
r = 8 cm

6. 11.5 Area of Circles & Sectors
HW pg. 758 #3­31 odds 6
March 31, 2014
Annulus:
region bounded by two concentric circles

7. 11.5 Area of Circles & Sectors
HW pg. 758 #3­31 odds 7
March 31, 2014
R = 12cm
r = 9 cm
r
60o
R
The shaded area is 12π cm2.
Find r.
r
120o

8. 11.5 Area of Circles & Sectors
HW pg. 758 #3­31 odds 8
March 31, 2014
11.5 HW pg. 758 #3-31 odds