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Radian, in geometry, metric unit for measuring angles, used to simplify calculations. The radian measure of an angle is the ratio a/r; a being the length of the arc intercepted by the given angle; and r being the radius of the circle. An angle of approx. 57.3 (or 360° divided by 2 pi) = 1 radian.

See also: Angles.

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21st Century Webster's Family Encyclopedia21st Century Webster's Family Encyclopedia - Providence to Rafflesia