A unit of plane angle measure equal to the angle subtended at the center of a circle by an arc equal in length to the radius of the circle. Note: One radian is equal to 360°/2 , which is approximately 57° 17' 44.6".
RADIAN (RAD.)
Meaning of RADIAN (RAD.) in English
Telecommunication standard terms English vocab. Английский словарь стандартных телекоммуникационных терминов. 2012