In the diagram, ED and GH are equal chords. Investigate the properties for equal chords in a circle by moving the sliders and clicking and dragging either of the blue points. What do you observe?

- Why is OD = OE = OG = OH?
- Given that ED and GH are equal chords, what test for congruent triangles will prove that triangles DOE and GOH are congruent?
- How can we use the result in (2) to prove the properties for equal chords in a circle?