Question

In the diagram below, Θ is measured in radians. Which equation represents the relationship between the radius, r, and arc length, s?

Circle O is shown. Line segments A O and B O are radii with length r. Angle A O B has a measure of theta. Arc A B has a measure of s.

s = Θ · r
r = Θ · s
s = Θ + r
r = Θ + s

Answer 1

s = Θ · r

Explanation: By definition of a radian, θ = s/r, so s = rθ.