Download 3.2-_trig_solving_4_missing_sides_and_angles

C
2
1. sin A 
5
2. cos A  21
5
2
2 21

3. tan A 
21
21
5
A
2
M
4. If C = 20º, then cos C is equal to:
A. sin 70
B. cos 70
C. tan 70
Skills Check
CCGPS Geometry
Day 39 (10-3-14)
UNIT QUESTION: What patterns
can I find in right triangles?
Standard: MCC9-12.G.SRT.6-8
Today’s Question:
How do we use trig ratios to find the
missing sides and angles of a
triangle?
Standard: MCC9-12.G.SRT.6-8
Using Trig to Find
Missing Angles
and Missing Sides
Finding a missing angle.
(Figuring out which ratio to use and an
inverse trig button.)
Ex: 1 Figure out which ratio to use. Find x. Round
to the nearest tenth.
O
20
tan   
20 m
40
1  20 
tan    x
 40 
  26.6
o
A
40 m
x
Shrink yourself down and
stand where the angle is.
Identify the given sides as
H, O, or A.
What trig ratio is this?
Ex: 2 Figure out which ratio to use. Find x. Round
to the nearest tenth.
O
15
sin   
15 m
50
1  15 
sin    x
 50 
  17.5
o
H
50 m
x
Shrink yourself down and
stand where the angle is.
Identify the given sides as
H, O, or A.
What trig ratio is this?
Ex. 3: Find . Round to the nearest degree.
17.2
tan  
9
O
17.2

9
A
 17.2 
tan 


 9 
1
  62
Ex. 4: Find . Round to the nearest degree.
A

7
23
H
7
cos  
23
 7 
cos    
 23 
1
  72
Ex. 5: Find . Round to the nearest degree.

200
O
H
200
sin  
400
 200 
sin 



 400 
1
  30
Finding a missing side.
(Figuring out which ratio to use and
getting to use a trig button.)
Ex: 6 Figure out which ratio to use. Find x. Round
to the nearest tenth.
x
tan 55 
20
20 m
55
A
20 tan 55  x
x  28.6 m
O
x
Ex: 7 Find the missing side. Round to the nearest
tenth.
O
80 ft
72
x
A
80
tan 72 
x
x tan 72  80
80
x
tan 72
x  26 ft
Ex: 8 Find the missing side. Round to the nearest
tenth.
x
O
H
283 m
24
x
sin 24  
283
283sin 24  x
x  115.1 m
Ex: 9 Find the missing side. Round to the nearest
tenth.
H
20 ft
40
x
A
x
cos40  
20
20 cos40  x
x  15.3 ft
When we are trying to find a
side we use sin, cos, or tan.
When we are trying to find
an angle we use (INVERSE)
-1
-1
-1
sin , cos , or tan .