is tаngent tо circle O аt B. Find the length оf the rаdius r fоr AB = 9 and AO = 13. Round to the nearest tenth if necessary. The circle has the center labeled O. A horizontal line segment AB lies at the top, touching the circle at point B, forming a tangent. A radius OB connects the center to the point of tangency, and this radius is labeled as "r". Another line segment OA extends from the center O through the circumference and beyond to the left, forming an extended radius. Together, segments OA and OB form triangle AOB.