1.4b cosine law find an angle.notebook
Learning Goal:
Minds On:
itself.
February 16, 2017
to find angles in an acute triangle using the cosine law
Rearrange the following equations to get x on one side by a) 6 = 14 ­ 4x
b) 82 = 42 + 52 ­ 20x
Now try to get cosC on one side by itself.
c2 = a2 + b2 ­ 2ab cosC
1
1.4b cosine law find an angle.notebook
February 16, 2017
Finding Angles Using the Cosine Law
Through a series of steps we can rearrange the cosine law formula to get the cosine of the angle on one side by itself.
c2 = a2 + b2 ­ 2abcos C rearranges to cos C = a2 + b2 ­ c2
2ab
We will use this formula when we are trying to find an angle using cosine law.
Find T.
R
7
6
S
?
T
8
2
1.4b cosine law find an angle.notebook
February 16, 2017
Solve ΔDEF.
D
12.8
E
13.5
10.6
F
3
1.4b cosine law find an angle.notebook
February 16, 2017
try p 39 # 2, 4, 6, 7 4