Radian (rad)
The radian (rad) is the SI unit of plane angle, the angle subtending an arc equal to the radius.
- Origin
- Defined geometrically from the circle, making it dimensionless in SI.
- Where it is used
- Used in structural analysis, rotation calculations and all trigonometric software input.
- Relation to SI
- 1 rad = 180/π degrees, about 57.2958°.