Math 120 Notes 8.4 – Reference Angles
I.
II.
Finding other values of the trigonometric function using the Reference Angle Approach
A.
What’s a reference angle and how can you use it to help you figure out a trig function? What is the
sign of the trig functions in each quadrant?
B.
Find the reference angle and then compute the exact value of sin  , cos  , and tan  .
1.
210°
2.
690°
3.
–240°
4.
7
6
5.
33
4
6.

2
3
Other points
A.
B.
A point on the terminal side of an angle is given. Find the exact value of each of the six trigonometric
functions. Be mindful of your signs!
1.
(21, -20)
2.
(-15, -8)
Here, you are given the value of one of the functions and the quadrant of the angle. Use this
information to find the other five trig ratios. Be mindful of your signs!
1.
sin  
5
, quadrant II
13
2.
cot  
7
, quadrant III
24
3.
cos  
2
, tan   0
3