Radian-scale protractors measure angles in radians. Angular displacement may be measured in radians or degrees. The curvature is the reciprocal of the curvature angular radius in radians. Angles expressed in radians are dimensionless for the purposes of dimensional analysis. The angular frequency formula 117 represents the frequency in radians per second. The phase axis is in either degrees or radians. Mathematically, this represents an arc of angle swept around a sphere by radians. The angle may be stated in degrees with an implied conversion from degrees to radians. The angular frequency has units of radians per second. When measuring angular speed, the unit radians per second is used. Thus, to convert from radians to degrees, multiply by 180/. The Moon is seen from Earth at an average angular diameter of 9.22 radians. A complete turn is thus an angle of radians. It is commonly measured in degrees per second or radians per second. Most allow a choice of angle measurement methods&colon; degrees, radians, and sometimes gradians.