Cambridge IGCSE Additional Mathematics · Syllabus 0606 · Circular Measure
Arc Length
What is Arc Length?
The distance measured along the curved edge of a circle between two points on it, equal to the radius multiplied by the central angle the arc subtends when that angle is measured in radians, written s = r theta. It is a length and therefore carries linear units such as centimetres. The formula is a direct rearrangement of the definition of the radian and is not supplied in the examination formula list, so it must be recalled; it is invalid for an angle given in degrees.
This definition is part of the Circular Measure chapter in Cambridge IGCSE Additional Mathematics.