Reference Angles

Front

What is a reference angle?

Back

A reference angle is the acute angle formed by the terminal side of an angle in standard position and the x-axis.

Front

How do you find the reference angle for an angle in standard position?

Back

To find the reference angle, subtract the angle from 180° if it's in the second quadrant, subtract 180° from the angle if it's in the third quadrant, or subtract the angle from 360° if it's in the fourth quadrant.

Front

What is the reference angle for 125°?

Back

55°

Front

What is the reference angle for -30°?

Back

30°

Front

What is the reference angle for -310°?

Back

50°

Front

What is the reference angle for 240°?

Back

240° - 180° = 60°.

Front

What is the reference angle for 450°?

Back

450° - 360° = 90°.

Front

What is the reference angle for 330°?

Back

360° - 330° = 30°.

Front

What is the reference angle for -150°?

Back

360° - 150° = 210°, then 210° - 180° = 30°.

Front

What is the reference angle for 210°?

Back

210° - 180° = 30°.