http://www.mathopenref.com/reference-angle.html Definition: The smallest angle that the terminal side of a given angle makes with the x-axis.

Assuming a base side for the angle along the X-axis, the reference angle is the smallest acute angle as measured from the X-axis

For ##290^o## it is ##70^o##

(yes; I know this is not technically an acute angle, but it is the smallest positive angle).

http://www.mathopenref.com/reference-angle.html Definition: The smallest angle that the terminal side of a given angle makes with the x-axis.

Assuming a base side for the angle along the X-axis, the reference angle is the smallest acute angle as measured from the X-axis

For ##290^o## it is ##70^o##

(yes; I know this is not technically an acute angle, but it is the smallest positive angle).