The document discusses different geometric shapes related to circles such as sectors, segments, and annuli. It provides formulas for calculating the areas of circles, sectors, and annuli. Examples are given for finding missing values like the radius or area given parts of the geometric shape and measurements.

1. 11.5 Area of Sectors March 21, 2013
Bellwork
8.64 cm
about 56.5 cm.
100.53 cm
7.64 ft
Mar 7­10:42 AM
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2. 11.5 Area of Sectors March 21, 2013
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?
Mar 7­10:43 AM
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3. 11.5 Area of Sectors March 21, 2013
Find the area of the shaded region.
20 in
10 cm
Mar 7­10:46 AM
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4. 11.5 Area of Sectors March 21, 2013
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 πr2
360
o
120
r = 3 cm
o
60
r = 6cm
Mar 7­10:48 AM
HW pg. 758 #3­31 odds 4

5. 11.5 Area of Sectors March 21, 2013
Segment of a Circle:
region bounded by a chord of a circle
& the included arc
r = 8 cm
Mar 7­11:35 AM
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6. 11.5 Area of Sectors March 21, 2013
Annulus:
region bounded by two concentric circles
Mar 7­11:38 AM
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7. 11.5 Area of Sectors March 21, 2013
R = 12cm
r = 9 cm
R
r
60o
The shaded area is 12π cm2.
Find r.
120o
r
Mar 7­11:39 AM
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8. 11.5 Area of Sectors March 21, 2013
11.5 HW pg. 758 #3-31 odds
Mar 7­11:41 AM
HW pg. 758 #3­31 odds 8