Inscribed Angle: An angle is an inscribed angle if and only if its vertex lies on a circle and its sides contain chords of the circle. The measure of an inscribed angle is one half the measure of the arc that it creates.

Examples of Inscribed Angles

Non-Examples of Inscribed Angles

This angle is not inscribed
because although the angle's vertex lies on a circle, one of its sides does not
contain a chord of the circle.

This angle is not inscribed
because the angle's vertex does not lies on a
circle.