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Definition of: radian
(rā′dē·ən) noun Math.
1. An arc equal in length to the radius of the circle of which it is a part.
2. The angle subtended by such an arc: 2π radians = 360°, π radians = 180° or 1 radian = (180/π)° or 57° 17′ 44.80625″ +. [<RADIUS]
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