1. 5/17 Geometry Bell Ringer A circle has an area of 64π sq. in.
What is the circumference?
Draw a picture of this circle with the radius labeled.
Homework: DUE FRIDAY:
p. 451 (#1 – 8, 11 – 14)
p. 455 (#1, 3, 6, 7, 9, 11)

2. 5/17 News and Notes Perfection: 8th Period Missing Quizzes:
1st: Tracia, LaFontae, Brandey
7th: Good.
8th: Desirae, Arely, Diego
Tutoring TOMORROW

3. Take 3 minutes and try to solve on your own or with person next to you
Find the distance from A to B by going around the circle. A B

4. So what’d you do?
Found the circumference of the whole circle.
Divided by two (or multiplied by 0.5)

5. What’d you just find? You found the length of an arc.
Arc – A part of the distance around a circle.
In this case, your arc was half of the circle. B

6. Example #1 Step 1: Find circumference of circle C = 2πr C = 2π * 18
C = 36π cm
Step 2: Find measurement of arc’s angle
Step 3: m Arc / 360
Step 4: Multiply together

7. Step 2: Find measurement of arc’s angle
360 – 150 = 210°
Step 2b: m Arc / 360  How much of the circle?
210/360
Step 3: Multiply together

8. To Review To find an arc length, you must know 3 things:
1. Circumference
2. How much out of 360° is the arc?
3. Multiply together

9. Guided Practice – Beat the clock!
Find length of CD
#1 – Find C
C = 2πr
C = 2π(10)
C = 20π inches
#2 – Find arc fraction
90/360 = 0.25
#3 – Find arc length D
r = 10 in. A

10. Independent Practice
Remember that the RADIUS is the key that unlocks everything!!!!

11. Exit Ticket 1. Find the length of AB
2. What did you learn about today? Be as precise as possible.