13.6.notebook
March 12, 2013
Problem of the Day 3/12/13
Solve triangle ABC with given parts:
1. A=75o, B=82o, c=16
2. B=131o, b=52, c=38
13.6
Objective(s):
Solve triangles using the law of cosines
Use Heron's formula to find a triangle's
area.
CCSS: F.TF.
1
13.6.notebook
March 12, 2013
Law of Cosines
Can be used for SAS & SSS triangles
a2=b2+c2­2bc cosA
b2=a2+c2­2ac cosB
c2=a2+b2­2ab cosC
B
a
c
A
b
C
ex: Solve triangle ABC with a=11, c=14, B=34o
a2=b2+c2­2bc cosA
b2=a2+c2­2ac cosB
c2=a2+b2­2ab cosC
GP:1
2
13.6.notebook
March 12, 2013
ex: Solve triangle ABC with a=12, b=27, c=20.
a2=b2+c2­2bc cosA
b2=a2+c2­2ac cosB
c2=a2+b2­2ab cosC
GP:2
Heron's Area Formula
Area= √s(s­a)(s­b)(s­c)
s=(1/2)(a+b+c)
ex: Find the area of the triangle.
350
170
240
GP: 4-6
3