The length of an arc is 10cm. find the angle subtending by the arc if the circumference of the circle of which the arc forms part is 60cm. (answer)
Using circumference = 2*pie*r and given that the circumference is 60cm you are able to solve for your "r" value. Then use arc length = r*theta solve for "theta" using the value you got from the previous step and the arc length you where given.