Reference Angles and Trig

What is the reference angle for -143^o?

• -37 degrees

• 37 degrees

• 143 degrees

• 53 degrees

Answer explanation

Our angle is less than 0 degrees, so we need to find a coterminal angle by adding 360 degrees (this gives us 217 degrees). This is a 3rd quadrant angle, so the reference angle is 217 - 180 degrees (or 37 degrees).

• 12 degrees and 348 degrees

• 12 degrees and 168 degrees

• 12 degrees and 192 degrees

• 168 degrees and 192 degrees

Answer explanation

These are the 1st and 3rd Quadrant angles (where tan > 0) that have a reference angle of  $\tan^{-1}\left(0.213\right)$  

• 249 degrees and 291 degrees

• 111 degrees and 291 degrees

• 111 degrees and 249 degrees

• 69 degrees and 111 degrees

Answer explanation

These are the 2nd and 3rd Quadrant angles (where cos < 0) that have a reference angle of  $\cos^{-1}\left(0.359\right)$  

Which of the following is a reference angle for 312^o

• 78

• -48

• -78

• 48

Which of the following is a reference angle for 236^o

• 54

• 56

• 74

• 36

Which of the following is a reference angle for -120^o

• 30

• 60

• 240

• 20

Which of the following is a reference angle for 158^o

• 22

• 58

• 202

• -202

Which of the following is a reference angle for 117^o

• 297

• 57

• 83

• 63

Evaluate: cos(-225^o)

• -(sqrt 2)/2

• (sqrt 2)/2

• sqrt 2

• 2

Evaluate: tan(330^o)

• -(sqrt 3)/3

• sqrt 3

• -(sqrt 3)

• 1