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3. Angles Subtending the Same Arc

Points A, B, C and D all lie on the circumference of the circle. Some of the points are connected by chords as shown. Point I is the intersection of chord CB and AD. What do you notice about and ? Move around points C and D. What impact does this have on the two angles? Can you infer the relationship between and ? Mark the check box and move around the points to confirm the relationship between the two angles. Given what you know about the angles, what can you deduce about and ?