Reference Angles!

~A reference angle is the same thing as a reduced fraction, it must be between 0 and 90 degrees.

~First: you find the original angle's quadrant.
~Second: you sketch the angle.
~Third: you see if the angle is positive or negative using the unit circle.
~Fourth: you subtract either 360 or 180 until the number is between 0 and 90 degrees.
__________________________________________________________________________

Ex.1 Find a reference angle of tan123 degrees.

tan=y/x; -ve/+ve= -ve.
123-180=-57
A reference angle of tan123 would be -tan57.

Ex.2 Find a reference angle of sin240 degrees.

sin=y/r; y: -ve.
240-180=60
A reference angle of sin240 would be -sin60.