Inscribed Angles
by Sofia Arcoy
Observe Angles DBE and DCE, and their relationship to Angle DAE.
The Inscribed Angle Theorem states that: The measure of the central angle is equal to twice the measure of the inscribed angle subtended by the same arc.
In this case, Angles DBE and DCE are inscribed angles that measure one-half of Angle DAE (Given that they all subtend the same Arc: Arc DE). Also, since the two inscribed angles subtend the same arc, then their measures are equal.