1. Law of Sines
January 14, 2014
The Law of Sines
Objecves:
1. To apply the Law of Sines
2. To develop problem‐solving skills.
The Law of Sines can be used to find missing parts of any triangles!
Law of Sines
In ΔABC: a, b, & c represent
the measures of the sides
opposite the angles with
measures A, B, & C.
THEN:
sin A = sin B = sin C
a
b
c
C
a
b
A
c
B
The Law of Sines can be used to solve a triangle in the following cases:
Case 1: You know the measure of two angles and any side
of a triangle.
What is looks like:
Case 2: You know the measures of 2 sides and an angle
opposite one of these sides of the triangle.
What is looks like:
Apr 30­9:18 AM
HW worksheet
1

2. Law of Sines
January 14, 2014
Find b. Round to the nearest tenth.
C
68o
3
37o
A
B
b
Triangle Area
You can find the area of a triangle by using the follwing:
A = 1/2 ab sinC
where a & b are the lengths of 2 sides and C is the angle
between these two sides.
b
h
C
a
Find the area
9
50o
18
Apr 30­9:37 AM
HW worksheet
2

3. Law of Sines
January 14, 2014
Find p. Round to the nearest tenth.
Then, find the area of ΔPQR
Q
8
P
17o
29o
R
What is the area of ΔLMN if n = 7, l = 9, and
measure of angle N = 43o?
Apr 30­9:32 AM
HW worksheet
3

4. Law of Sines
January 14, 2014
A house is built on a triangular plot of land. Two sides of the
plot are 160 feet long, and they meet at an angle of 85 o. If a
fence is to be placed along the perimeter of the property, how
much fencing materials is needed?
How many square feet of property does the landowner possess?
Apr 30­9:52 AM
HW worksheet
4

5. Law of Sines
January 14, 2014
HW: Law of Sines Worksheet
May 9­7:50 AM
HW worksheet
5