Warm up: Solve for x

18◦

1.)

x

124◦70◦

x

2.)

3.)

x

260◦

20◦110◦ x

4.)

53 145

8070

Skills Chec

k

Circumference & Arc Length

of Circles

2 Types of AnswersRounded• Type the Pi

button on your calculator

• Toggle your answer

• Round

Exact• Type the Pi

button on your calculator

• Pi will be in your answer

• TI 36X Pro gives exact answers

CircumferenceThe distance around a circle

orC 2 r

C d

Circumference

Find the EXACT circumference.

28 ft1.r = 14 feet

2.d = 15 miles15 miles

C 2 14

C 15

Ex 3 and 4: Find the circumference. Round to the nearest tenth.

89.8 mm 103.7 ydC 2 14.3 C 33

5. A circular flower garden has a radius of 3 feet. Find the circumference of the garden to the nearest hundredths.

C = 18.85 ft

r2 C C 2 3

Arc LengthThe distance along the curved line

making the arc (NOT a degree amount)

Arc Length

measure of arcArc Length 2

360r

Ex 6. Find the Arc LengthRound to the nearest hundredths

8m

70

Arc Length 9.77 m

measure of arcArc Length 2

360r

70

Arc Length 2 8360

Ex 7. Find the exact Arc Length.

10Arc Length in3

measure of arcArc Length 2

360r

120

Arc Length 2 5360

Ex 8 Find the radius. Round to the nearest hundredth.

B

A

»Arc Length of 3.82AB m=

60◦

3.65 mr

60

3.82 2360

r

1375.2 60 2 r

1375.2 120 r11.46 r

Ex 9 Find the circumference. Round to the nearest hundredth.

80◦

8032.11 2

360r

11,559.6 80 2 r

144.50inC

»Arc Length of 32.11inAB=

B

A

11,559.6 80 C

Ex 10 Find the radius of the unshaded region. Round to the nearest tenth.

75◦ B

A

»Arc Length of 10AB cm=

75

10 2360

r

3600 75 2 r3600 150 r

24 r7.6r cm

Group WorkDon’t get stumped, ask your

group members for help.