The two arc lengths shown on the circles are equal, but the circles are different sizes. 2 circles. One circle has a radius of 8 inches and a shaded sector with an angle measure of 90 degrees. The second circle has a shaded sector with an angle measure of 120 degrees. One circle has a radius of 8 in. What is the radius of the other circle? Arc length circle 1 = Arc length circle 2 StartFraction 90 degrees over 360 degrees EndFraction (2 pi (8)) = StartFraction 120 degrees over 360 degrees EndFraction (2 pi (4)) One-fourth (16 pi) = one-third (2 pi r) 4 = two-thirds r r =