1. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Page 521 and 594
18) 15
19)
𝟑 𝟓
20)
𝟐 𝟏𝟎
21)
𝟐 𝟓
22)
𝟑 𝟐
23)
𝟑 𝟓 𝟏𝟎
11)
1.25 m
12)
(4x + 2) in
13)
21x2 + 32x – 5 ft2
14)
𝟐𝟏𝟎 𝒊𝒏𝟐
15)
𝒉=𝟐𝟎𝒄𝒎
16)
𝟒𝒙𝟐+𝟒𝒙 𝑓𝑡2
17)
𝟏𝟗𝟔 𝟑 𝒊𝒏𝟐
18)
6x ft 2
19)
12x x + 20 ft2
23)
𝟑𝟎 𝟑 𝒄𝒎𝟐
24)
𝟑𝟎 𝒎𝟐
25)
𝟑𝟎𝟎 𝒊𝒏𝟐
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

2. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

3. Perimeter and Area of Circles and Sectors
Section 9–2 and 11-3
Geometry PreAP, Revised ©2014
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

4. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Formulas
Area of Circle: 𝑨=𝝅 𝒓 𝟐
Circumference of Circle: 𝑪=𝟐𝝅𝒓
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

5. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Example 1
Find the area of K in terms of π.
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

6. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Example 2
Find the circumference of M if the area is 25 x2 π ft2
A = r2
C = 2r
25x2 = r2
C = 2(5x)
25x2 = r2
C = 10x ft
5x = r
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

7. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Your Turn
Find the area in terms of π in which C = (4x – 6)π m.
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

8. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Arc Length
the length of an arc is a fraction of the circumference of the circle
Arc Length: 𝑳=𝟐𝝅𝒓 𝒎 𝟑𝟔𝟎 where m is the given angle
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

9. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Example 3
Find the arc length with a measurement of 40 and the radius is 6 m. Give answers in terms of  and rounded to the nearest ten-thousandth, if necessary.
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

10. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Example 4
Determine the angle measurement, when the arc length is 32/45  inches and the diameter is 16 inches. Give answers in terms of  and rounded to the nearest ten-thousandth, if necessary.
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

11. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Your Turn
Determine the radius, when the arc length is 2/3  inches and the measurement of the angle is 18. Give answers in terms of  and rounded to the nearest ten-thousandth, if necessary.
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

12. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Sector Area
The area of a sector is a fraction of the circle containing the sector.
Sector Area of a Circle: 𝑨=𝝅 𝒓 𝟐 𝒎 𝟑𝟔𝟎 where m is the given angle
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

13. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Example 5
Find the area of sector ABC. Give answers in terms of  and rounded to the nearest ten-thousandth.
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

14. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Example 6
Identify the radius of a circle if the sector area is 1/16  ft2 and the angle sector area is 90 degrees. If needed, rounded to the nearest ten-thousandth.
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

15. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Example 7
Determine the angle measure if the sector area is 4  in2 and the radius is 6 inches. If needed, rounded to the nearest ten-thousandth.
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

16. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Your Turn
Identify the radius of a circle if the sector area is 1/32 ft2 and the angle sector area is 180 degrees. If needed, rounded to the nearest ten-thousandth.
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9-2 and 11-3: Perimeter and Area of Circles and Sectors

17. 9-2 and 11-3: Perimeter and Area of Circles and Sectors
Assignment
Page 603: 10-12, 40 Page 767: 19–21, 27 (leave answers in pi)
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9-2 and 11-3: Perimeter and Area of Circles and Sectors