This document contains notes from a math class on the topics of arc lengths and circumference. It includes formulas for calculating circumference of circles and arc length. Several example problems are worked through applying these formulas, such as finding the radius of a circle given the length of an arc, and calculating arc lengths within circles given measurements of the arcs in degrees.

1. 11.4 Arc Lengths
HW pg. 749 #4­26 evens
March 31, 2015
Bellwork
Figure I ~ Figure II. Find the ratio of the perimeters and the
ratio of the areas. Then find the unknown area.
Ratio of perimeters: 4:3;
ratio of areas: 16:9;
Unknown Area :33.75 ft2
2. Rectangle I ~ Rectangle II.
In Rectangle I, the length is 20 feet & the perimeter is 64 feet.
In Rectangle II, the width is 8 yards.
Find the ratio of the area of Rectangle I to the area of Rectangle II.
144 : 576
1 : 4

2. 11.4 Arc Lengths
HW pg. 749 #4­26 evens
March 31, 2015
Circumference of a Circle:
C = 2πr (Twinkle­twinkle)
11.4 Circumference & Arc Length
The circumference of a circle is 28 π. What is the area of the circle?

3. 11.4 Arc Lengths
HW pg. 749 #4­26 evens
March 31, 2015
Arc Length: fraction of a circle's circumference
xo
360 *circumference where x = the arc measure
60
o
A
BC
4in
Length AB = ____
D
N
M
C
6.5 yd
280o
Length minor arc
MN = ____

4. 11.4 Arc Lengths
HW pg. 749 #4­26 evens
March 31, 2015
N
M
P
22
cm
Q
Arc QN = 60 o
Find the length of arc NM.
M
500
Q
diameter = 9 ft
Length of QM = _______
120oA
B
r
The length of AB is 6π. Find the radius.

5. 11.4 Arc Lengths
HW pg. 749 #4­26 evens
March 31, 2015

6. 11.4 Arc Lengths
HW pg. 749 #4­26 evens
March 31, 2015
11.4 HW pg. 749 #4­26 evens