A unit of measure for angles. One radian is defined as the measure of a central angle whose sides cut off an arc equal in length to the radius on the circumference of the circle. Since the length of this arc is equal to one radius of the circle, the measure of this angle is said to be one radian.

symbol space1 radian = (180/symbol PI)° = 57.296°

The advantage of radians over degrees is simply that it can help simplify many trigonometric formulas.

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