Central Angle
The angle formed by two radii of a circle or by two rays with the same endpoint. The vertex of the angle formed is at the centre of the circle.
If two intersecting lines meet at the centre of a circle, they form a central angle.
Example
In the figure below, angle AOB is a central angle of the circle with centre O.
Property
The degree measure of a central angle is equal to the degree measure of its intercepted arc.
m[latex]∠\textrm{AOB}[/latex] = m[latex]\widehat{\textrm{AB}}[/latex]