A central angle is an angle with its vertex at the center of a circle, with its sides containing two radii of the circle.
In the figure above, , and are central angles.
Sum of Central Angles: The sum of the measures of the central angles of a circle with no points in common is .
For example, in the figure above,
Find the value of .
The sum of the measures of the central angles of a circle with no interior points in common is . So,
Subtract from each side.