In higher classes, we don’t use degree to measure angles
We use radians.
We define radian in terms of length of arc :
Angle subtended by an arc of 1 unit in a circle of radius 1 unit is 1 radian .
In other words,
- If length of arc is 1 unit
- & Radius = 1 unit
- Then, angle at center = 1 radian
Note: In θ = l/r i.e. length of arc formula,
Angle is measured in radians