Radian

A radian is a way to measure angles based on the radius of a circle. Specifically, one radian is the angle created when the length of the arc (curved part of the circle) equals exactly the radius of the circle. Since the entire circle has a circumference of about 6.28 times its radius, it contains approximately 6.28 radians. Radians are useful in mathematics and physics because they relate angles directly to the properties of circles, simplifying calculations involving rotations and oscillations without relying on degrees.