Co-terminal and Reference Angles

Front

What is a reference angle?

Back

A reference angle is the acute angle formed by the terminal side of an angle and the x-axis, always measured as a positive angle.

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 degrees if it's in the second quadrant, or subtract 360 degrees if it's in the fourth quadrant. For angles in the first quadrant, the reference angle is the angle itself.

Front

What is the reference angle for 150 degrees?

Back

60 degrees.

Front

What is the reference angle for 420 degrees?

Back

60 degrees.

Front

What is the reference angle for -330 degrees?

Back

30 degrees.

Front

What is the reference angle for -120 degrees?

Back

60 degrees.

Front

What are coterminal angles?

Back

Coterminal angles are angles that share the same terminal side when drawn in standard position, differing by full rotations of 360 degrees.

Front

How do you find a coterminal angle?

Back

To find a coterminal angle, add or subtract multiples of 360 degrees from the given angle.

Front

What is a coterminal angle for 150 degrees?

Back

510 degrees (150 + 360).

Front

What is a coterminal angle for -30 degrees?

Back

330 degrees (-30 + 360).