1. Unit 9. Day 8.

2. We want the area of the circle
𝐶=𝜋∙𝑑 𝐶
𝐶=𝜋∙ 2𝑟 2 𝐶 =
𝜋∙𝑟
𝜋∙𝑟 𝑟 𝑟
𝑟 2
We will find the area of this “rectangle” 𝐴= 𝜋∙
𝑏∙ℎ
𝑙∙𝑤 ∙ 𝑟

3. Example A: Find the area of the circle. 𝜋≈3.1415926… 𝐴=𝜋∙ 𝑟 2
22 7
𝜋≈ … 𝜋
3.14
𝐴=𝜋∙ 𝑟 2
7 𝑐𝑚
7 𝑐𝑚
7 𝑐𝑚
7 𝑐𝑚
𝐴= ∙
𝐴= 𝜋 ∙ 49 𝑐𝑚 2
𝐴=49𝜋 𝑐𝑚 2
𝐴=𝜋∙ 𝑟 2
𝐴=𝜋∙ 𝑟 2
𝐴= ∙
𝐴= ∙
𝐴≈ ∙
𝑐𝑚 2 7
49 𝑐𝑚 2
𝐴≈ 3.14 ∙ 49 𝑐𝑚 2 1
𝐴 ≈ 𝑐𝑚 2
𝐴≈154 𝑐𝑚 2

4. Example B: Find the area of the circle. 𝜋≈3.1415926… 𝐴=𝜋∙ 𝑟 2
22 7
𝜋≈ … 𝜋
3.14
𝐴=𝜋∙ 𝑟 2
4 𝑖𝑛
8 𝑖𝑛
4 𝑖𝑛
4 𝑖𝑛
𝐴= ∙
𝐴= 𝜋 ∙ 16 𝑖𝑛 2
𝐴=16𝜋 𝑖𝑛 2
𝐴=𝜋∙ 𝑟 2
𝐴=𝜋∙ 𝑟 2
𝐴= ∙
𝐴= ∙
𝑖𝑛 2
𝐴≈ ∙
16 𝑖𝑛 2
𝐴≈ 3.14 ∙ 16 𝑖𝑛 2
𝐴≈ 𝑖𝑛 2
≈ 𝑖𝑛 2
𝐴 ≈ 𝑖𝑛 2

5. Example C: A sprinkler rotates in a circular pattern and sprays water over a distance of 12 feet. What is the area of the circular region covered by the sprinkler? Express your answer to the nearest square foot.
Example D: Suzanne is making a circular table out of a square piece of wood. The square is 6 ft by 6 ft, and Suzanne wants to cut as big a circle as possible. How much waste will she have for this project? Express your answer to the nearest square foot.

6. Example C: A sprinkler rotates in a circular pattern and sprays water over a distance of 12 feet. What is the area of the circular region covered by the sprinkler? Express your answer to the nearest square foot.
𝜋≈ …
3.14
𝐴=𝜋∙ 𝑟 2
𝐴= ∙
𝐴≈ 3.14 ∙ 144 𝑓𝑡 2
𝐴 ≈ 𝑐𝑚 2
12 𝑓𝑡
12 𝑓𝑡

7. Example D: Suzanne is making a circular table out of a square piece of wood. The radius of the circle that she is cutting is 3 feet. How much waste will she have for this project? Express your answer to the nearest square foot. 𝐴=
36 𝑓𝑡 2
𝜋≈ …
3.14
𝐴=𝜋∙ 𝑟 2
6 𝑓𝑡
𝐴= ∙
𝐴≈ 3.14 ∙ 9 𝑓𝑡 2
𝐴 ≈ 𝑓𝑡 2
3 𝑓𝑡
3 𝑓𝑡
6 𝑓𝑡 36 −
28.26
7.74
𝑓𝑡 2
≈8 𝑓𝑡 2