Which of the following statements is true?

A reference angle may be obtuse.
A reference angle is always acute.
A reference angle is between 0 and 180 degrees.
A reference angle can be negative.

Respuesta :

A reference angle is always acute.

Reference angles are formed by 
the terminal side of theta and the horizontal axis. Since reference angles are always between 0° and 90°, they are always acute angles.
A reference angle is always acute