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Formula Angle (Definition) Arc length    Radius

Formula
Formula: Angle (Definition)
Arc Length, Angle and Radius of a Circle

Angle

Unit
The angle (e.g. measured from the horizontal axis) is defined as the arc length \(s\) per radius \(r\).

Radian is a dimensionless unit. \(1\,\text{rad}\) corresponds to the angle at which the arc length \(s\) is exactly as long as the radius \(r\).

Arc length

Unit
A section of the circumference of the circle.

Radius

Unit
Radius of a circle. In other words, the distance from the center of the circle to the circle's line.