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Right Triangles

Angles in Standard Position

Sine Law & Ambiguous Case

Cosine Law

Problem Solving

Summary&Test

 

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UNIT 6  : BASIC TRIGONOMETRY WITH TRIANGLES

 LESSON 3:  SINE LAW HOMEWORK QUESTIONS PAGE 2  (Solutions below)

 

Quick Review: (Solutions below)

         

                         

                                            C                                                

 

 

 

                 b                 h            b              a   

 

 

 

                A1                                                                             (        B

                                                D                        A2                                          

 

 

Text Box: Summary of main ideas:
·	Use the sine law when given 2 angles and a side (AAS) or two sides and a non-contained 
      angle (SSA).
·	For the SSA situation, where the given angle is acute; the ambiguous case occurs if the side opposite the given angle is the shorter of the two given sides.
·	To solve the triangle in this case, proceed as follows: 
1.	Calculate the height of the triangle (h = a sinB)
2.	If  b > h then there are two triangles
3.	If b = h there is one right triangle
4.	If b < h there is no triangle
·	For the SSA situation, where the given angle is acute; if the side opposite the given angle is the longer side, there is one solution.
·	For the SSA situation, where the given angle is obtuse; if the side opposite the given angle is the longer side, there is one solution
·	For the SSA situation, where the given angle is obtuse; if the side opposite the given angle is the shorter side, there is no solution
·	For the AAS situation, there is one solution.
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Homework Questions: (all measurements in cm. unless otherwise stated.  Give answers to the nearest tenth)

 

 

4. Determine all possible solutions for each of the triangles below.  Include a sketch.

 

 

Solutions for # 4:

 

 

                                            D                                    

                                             660         

 

 

                                                                  11.1          

 

 

 

                E                                                                                     F

                                                       12.7                                                                                                                        

 

This is the SSA case with < D acute; the side across from the given angle is the longer side. There is one triangle only.

           

First we must find a second angle.  Find < D since we know d.

           

           

 

 

 

                                                                 R

 

 

 

                             9.5              7.1         h                7.1

 

 

                      540

                P                      S                                               Q

 

 

 

                                                                 R

 

 

 

                             9.5                            h                7.1

 

 

                      540

                P                              r                                                    Q

 

 

 

This is the SSA case with < P acute; the side across from the given angle is the shorter side. This is the ambiguous case

First we calculate the height of the triangle since the shorter side (7.1) is opposite the given angle.

           

 

 

 

                                                                 R

 

 

 

                             9.5              7.1         7.7             7.1

 

 

                      540

                P                                                                       Q

 

 

 

 

 

                                                                 C

 

 

 

                            13.2             10.1       h                10.1

 

 

                      360

                A                     D                                               B

 

 

                                                                 C

 

 

 

                            13.2                         h                  10.1

 

 

                      360

                A                            c                                         B

 

 

This is the SSA case with < A acute; the side across from the given angle is the shorter side. This is the ambiguous case

First we calculate the height of the triangle since the shorter side (10.1) is opposite the given angle.

           

 

           

                                                                 C

 

 

 

                            13.2                   10.1          

 

 

                      360     129.80     

                A         c          D                                               

 

 

 

 

                                                                                                                                   

                                                                 D                                                               

 

 

 

                            14.1             11.4       h                11.4

 

 

                      43.20

                E                      G                                               F

 

 

                                                                 D

 

 

 

                            14.1                           h                11.4

 

 

                      43.20

                E                              d                                        F

 

 

This is the SSA case with < E acute; the side across from the given angle is the shorter side. This is the ambiguous case

First we calculate the height of the triangle since the shorter side (11.4) is opposite the given angle.

           

 

           

                                                                 D

 

 

 

                            14.1                   11.4          

 

 

                     43.20   122.10     

                E          d          G                                               

 

 

 

This is the AAS case.  There will be only one triangle.

 

                                                                 D

                                                              470

 

 

                                    f                                           8.4

 

 

                                                                               1020         

                E                              d                                        F

First find < E:  1800 – (1020 + 470) = 310

 

 

 

                                            A                                    

                                             1020       

 

 

                 c                                               7.9

 

 

 

                B                                                                                      C

                                                       10.6                                                                                                                        

 

This is the SSA case with < A obtuse; the side across from the given angle is the longer side. There is one triangle only.

           

First we must find a second angle.  Find < B since we know b.

           

 

 

 

 

                                            P                                     

                                             1210       

 

 

                  r                                                                   8.7                            

 

 

 

                Q                                                                                                                                 R

                                                                 4.1                                                                                                    

 

This is the SSA case with < P obtuse ; the side across from the given angle (1210) is the shorter side. There is no triangle possible.

           

 

 

                                            P                                     

                                             1210       

 

 

                  r                                                                   8.7                            

 

 

 

                Q                                                                                                                                 R

                                                                 4.1                                                                                                    

 

 

 

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