What is an angle whose vertex is the center of the circle?

An angle whose vertex is the center of a circle is called a central angle. The measure of a central angle is equal to the measure of the intercepted arc. A central angle always has its sides tangent to the circle at the endpoints of the intercepted arc. The degree measure of a central angle can range from 0° to 360°. If the central angle has a measure greater than 180°, it is called a reflex angle.