A chord of a circle is a line segment whose endpoints lie on the circle. An inscribed angle is the angle formed by two chords having a common endpoint. The other endpoints define the intercepted arc. The central angle of the intercepted arc is the angle at the midpoint of the circle.
The vertex of an inscribed angle can be anywhere on the circle as long as its sides intersect the circle to form an intercepted arc. The Inscribed Angle Theorem states that the measure of an inscribed angle is half the measure of its intercepted arc. Inscribed angles that intercept the same arc are congruent.
