What was the relation between the central angle and its intercepted arc?

• If the vertex of an angle exists in the center of the circle and the two sides of the angle are radii in the circle, then this angle exists named a central angle.
• Each central angle exists subtended by the opposite arc, the name of the arc exists the starting point and the finish point of the angle.
• There exists a relation between the central angle and its subtended arc the measure of the central angle equals half the measure of its subtended arc.
• The length of the subtended arc relies on the measurement of its central angle and the length of the radius and the measure of the arc.
• The measurement of the circle exists at 360°.
• The length of the circle exists at 2πr.