Reference Angles

Reference angles must be between 0 degrees and 90 degrees.

1. Find the quadrant of the number and sketch
2. Find wheather the angle is positive or negative
3. To get the number between 0 and 90 degrees subtract 360 degrees or 180 degrees

Ex. Find the reference angle.

A. Sin 225 degrees
Sin is y/r which is in the 3rd quadrant so it's negative. Subtract 225-180 which is 45. So the answer is -sin 45 degrees

B. Cos 300 degrees
Cos is x/r which is in the 4th quadrant so it's positive. Subtract 300-360 which is 60. So the answer is +cos 60 degrees

C. Tan 150 degrees
Tan is y/x which is in the 2nd quadrant so it's negative. Subtract 150-180 which is 30. So the answer is -tan 30 degrees