

Rules of Angles and Reference angle
Positive angles go in a counter clockwise direction. Below is a picture of a positive fifty degree angle Quadrant I
Every positive angle in quadrant I is already acute...so the reference angle is the measure of the angle itself:
Quadrant II
To find the reference angle measuring x ° for angle in Quadrant III, the formula is $$ 180  x^{\circ} $$ .
Quadrant III
To find the reference angle measuring x ° for angle in Quadrant III, the formula is $$ x  180 ^{\circ} $$ .
Quadrant IV
To find the reference angle measuring x ° for angle in Quadrant IV, the formula is $$360 ^{\circ} x $$ .
What is the reference angle for the angle in the graph below?
What is the reference angle for a 210° angle?
Word Problems
What is the reference angle for a 300° angle?
Problem 1) What is the reference angle for an angle that measures 91 ° ?
Problem 2) What is the reference angle for an angle that measures 250 ° ?
Further Reading
