Reference Angles and Triangles

                    Lesson 1

 

                                                            Problem:    The value of Sin 390 is equal to?

 

                                                                                              

                                                            Solution     The value of Sin 390 is equal to

                                                            Step 1:        

                           

                                                            Solution     The angle is one complete revolution plus 30.

                                                            Step 2:           

                            

                                                            Solution     Look at the triangle, it can be seen that Sin 390 = and that Cos 60

Step 3: (in the same triangle) is that same result.                                                             

 

                                                            Solution     Answer: Sin 390 = Cos 60

                                                            Step 4: 

Complete      

 

                                                            Try two practice problems:  

 

A.

The value of sin 420 is equal to ?

B.

Write sec -250 as a positive acute angle.

 

 

 

 

 

 

 

 

 

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