Math 9: Inscribed Angles
Inscribed angles are formed by two chords that share a common endpoint. Move any of points A, B, D, or E along the circle. What do you notice about the two angles? What happens if you move D or E onto the green arc?
Rule: Inscribed angles subtended by the same arc are congruent. Translation: angles on a circle that are across from the same arc will have the same angle.