7.2 day 1 2015.notebook
April 10, 2017
7
A
5
42
B
C
7.2 day 1 2015.notebook
April 10, 2017
C
solve the triangle.
A
7
5
42
B
Law of Cosines = use this law when given three sides or
two sides and the included angle.
a2 = b2 +c2 -2bc cosA
b2 = a2 +c2 -2ac cosB
c = a +b -2ab cosC
2
2
2
hint: In law of cosines
always solve for the
biggest angle first!
hint: In law of sines
always solve for the
smallest angle first if
possible!
7.2 day 1 2015.notebook
April 10, 2017
Solve the triangle.
C
b
a2 = b2 +c2 -2bc cosA
b2 = a2 +c2 -2ac cosB
A
a
c2 = a2 +b2 -2ab cosC
Solve the triangle.
a2 = b2 +c2 -2bc cosA
c
B
B = 42°
a=8
c=5
C
b
b2 = a2 +c2 -2ac cosB
A
a
c
B
C = 73°
a=4
b=8
c2 = a2 +b2 -2ab cosC
7.2 day 1 2015.notebook
April 10, 2017
Solve the triangle.
C
b
a2 = b2 +c2 -2bc cosA
b2 = a2 +c2 -2ac cosB
A
a
c
c2 = a2 +b2 -2ab cosC
hint: Always solve for the
biggest angle first!
B
a = 12
b = 14
c = 17
Solve the triangle.
C
b
b2 = a2 +c2 -2ac cosB
A
a
c
B
a = 25
b = 18
c = 23
a2 = b2 +c2 -2bc cosA
c2 = a2 +b2 -2ab cosC
hint: Always solve for the
biggest angle first!
7.2 day 1 2015.notebook
April 10, 2017
Area of a triangle.
6'
4'
7'
Heron's formula
b
a
where s is the semi-perimeter
c
Find the area of the triangle.
15"
8"
12"
7.2 day 1 2015.notebook
pg 661
1, 5, 9, 11, 17, 25, 27
April 10, 2017