The radian is the SI unit of angle, defined as the angle subtended at the center of a circle by an arc equal in length to the radius.
Proposed in 1873 by Scottish physicist James Thomson, it was adopted as the SI angle unit for its natural fit in mathematical calculations.
Measurement system: International System of Units (SI). SI equivalent: Base SI angle unit (2π rad = 360°).
Radian facts
- Unit name
- Radian
- Symbol
- rad
- Category
- Angle
- Measurement system
- International System of Units (SI)
- SI equivalent
- Base SI angle unit (2π rad = 360°)
- Common uses
- Trigonometry, engineering calculations, angular velocity and acceleration formulas
Definition of the radian
The radian is the SI unit of angle, defined as the angle subtended at the center of a circle by an arc equal in length to the radius.
Measurement system and SI relationship
International System of Units (SI)
SI equivalent: Base SI angle unit (2π rad = 360°)
History of the radian
Proposed in 1873 by Scottish physicist James Thomson, it was adopted as the SI angle unit for its natural fit in mathematical calculations.
Where is the radian used?
Trigonometry, engineering calculations, angular velocity and acceleration formulas