In order to find the arc length of AB, we need both the radius of the circle and the angle at the center subtended by the arc AB.
The length of an arc, either minor or major, can be calculated with the use of these formulas:
1) When the central angle is in radians:
Arc Length = Angle (in radians) x Radius
The formula explains that the arc length is just the proportion of the "whole" circumference (2πR), calculated as (angle/360) multiplied by the entire circumference.
2) When the central angle is in degrees:
Arc Length = (Angle/360) * 2 * π * Radius
We can't calculate the arc length of AB without knowing both the radius and the angle subtended by the arc AB.
As soon as these values are available, plug them into the appropriate formula and complete the calculation.