An is formed when two secant lines intersect on a circle. It can also be formed using a secant line and a tangent line intersecting on a circle A is an angle whose vertex is the center of the circle and whose sides pass through a pair of points on the circle, therefore subtending an arc. The of a circle consists of two points on the circle and all of the points on the circle that lie between those two points.
The measure of an angle inscribed in a circle is the measure of the Note that this is equivalent to the measure of the inscribed angle is half the measure of the central angle if they intercept the same arc.