Trigonometric Ratios Worksheet Page 16

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Example
Determine the length of f to one decimal place.
D
19.5 m
f
F
118°
12.6 m
E
Solution
Two side lengths and one angle measure are given. Check for the ambiguous case.
Side e is opposite the known angle.
Since e > d, only one triangle is possible.
Determine ∠D.
sin D
sin E
_____
_____
      =    
   
e    
d
sin D
sin 118°
_____
_______
     =    
   
   
12.6
19.5
12.6 sin 118°
___________
sin D =    
19.5
(  
)
12.6 sin 118°
___________
     ∠ D = sin
–1
  
   
   
19.5
          =  34.7864…°
   
  � �  34.8°
34.8°
Determine ∠F.
∠F = 180° − (118° + 34.8°)
= 27.2°
Determine f.
f
e
_____
_____
      =    
         
 
 
   
sin F
sin E
f
19.5
________
_______
      =    
   
 
   
sin 27.2°
sin 118°
19.5 sin 27.2°
___________
       f =    
   
sin 118°
        = 10.0950…
   
� 10.1
The length of side f  is approximately 10.1 m.
16  MHR  •  Chapter 1  978-0-07-090893-2
  Printer Pdf

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