Source: wikibot/circular-measure
= Circular measure
{wiki=Circular_measure}
Circular measure, also known as radian measure, is a way of measuring angles based on the radius of a circle. In this system, an angle is defined by the length of the arc it subtends on a circle with a radius of one unit. The key ideas in circular measure include: 1. **Radians:** The primary unit of circular measure is the radian. One radian is defined as the angle that subtends an arc of length equal to the radius of the circle.