Circumference & Arc Length

of Circles

2 Types of Answers

Rounded• Put mode on

classic• Type the Pi

button on your calculator

• Round

Exact• Put mode on

mathprint• Type the Pi

button on your calculator

• Pi will be in your answer

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 yd

C 2 14.3 C 33

Work on 5 & 6 in partners.

Arc LengthThe distance along the curved line

making the arc (NOT a degree amount)

Arc Length

measure of arc

Arc Length 2360

r

Ex 7. Find the Arc LengthRound to the nearest hundredths

8m

70

Arc Length 9.77 m

measure of arc

Arc Length 2360

r

70

Arc Length 2 8360

Ex 8. Find the exact Arc Length.

10Arc Length in

3

measure of arc

Arc Length 2360

r

120

Arc Length 2 5360

Ex 9. 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 r

11.46 r

Ex 10. 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 11. 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 r

3600 150 r

24 r7.6r cm

FYI: Unit 3A Test

Next Tuesday!