This document discusses formulas and examples for calculating the areas of circles, sectors, segments, and annuli. It introduces the formula for calculating the area of a circle as πr^2. It then provides examples of using this formula, as well as the formula for calculating the area of a sector, which is (portion of the circle) x (area of the circle). The document concludes by assigning homework problems from page 758 numbers 3 through 31 odds.

1. 11.5 Area of Circles & Sectors March 07, 2012
Bellwork
about 56.5 cm.
8.64 cm
100.53 cm
7.64 ft
HW pg. 758 #3­31 odds 1

2. 11.5 Area of Circles & Sectors March 07, 2012
11.5 Areas of Circles & Sectors
Area of Circle = πr2 (fuzzy wuzzy)
4.2 m
A circle has an area of ≈ 38.485 in2.
What is the circumference of the circle?
HW pg. 758 #3­31 odds 2

3. 11.5 Area of Circles & Sectors March 07, 2012
Find the area of the shaded region.
20 in
10 cm
HW pg. 758 #3­31 odds 3

4. 11.5 Area of Circles & Sectors March 07, 2012
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 πr
2
360
o
120
r = 3 cm
o
60
r = 6cm
HW pg. 758 #3­31 odds 4

5. 11.5 Area of Circles & Sectors March 07, 2012
Segment of a Circle:
region bounded by a chord of a circle
& the included arc
r = 8 cm
HW pg. 758 #3­31 odds 5

6. 11.5 Area of Circles & Sectors March 07, 2012
Annulus:
region bounded by two concentric circles
HW pg. 758 #3­31 odds 6

7. 11.5 Area of Circles & Sectors March 07, 2012
R = 12cm
r = 9 cm
R
r
60o
The shaded area is 12π cm2.
Find r.
120o
r
HW pg. 758 #3­31 odds 7

8. 11.5 Area of Circles & Sectors March 07, 2012
11.5 HW pg. 758 #3-31 odds
HW pg. 758 #3­31 odds 8