Question

How do you define one radian?

Answer 1

1. The radian, denoted by the symbol $rad,$ is the SI unit for measuring angles, and is the standard unit of angular measure used in many areas of mathematics.
2. The radian is defined in the SI as being a dimensionless unit with $1rad=1.$
3. One radian is defined as the angle subtended from the centre of a circle which intercepts an arc equal in length to the radius of the circle.
4. More generally, the magnitude in radians of a subtended angle is equal to the ratio of the arc length to the radius of the circle; that is, $\theta =\frac{s}{r}$ where $\theta$ is the subtended angle in radians, $s$ is arc length, and $r$ is the radius.
5. One radian is the measure of a central angle subtended by an arc that is equal in length to the radius of the circle.
6.