Radian
Also: rad
An angle unit defined by arc length divided by radius.
One full turn is 2π radians; radian measure makes derivatives and angular equations take their standard form.
- Units
- radian (rad), dimensionless
- Formula
θ = s/r
Example A 90° quarter-turn equals π/2 radians.
Common misconception A calculator in radian mode will not interpret the number 60 as 60 degrees.