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Angles at the circumference

Investigate the circle property by clicking and dragging any of the blue points. What observation can you make regarding the angles at the circumference? Confirm your conjecture by revealing the relevant measurements then show the property.

1. What is the relationship between <AOB and the angles at the circumference?
2. What property describes the relationship in question (1)?
3. What is the size of each of the angles at the circumference when <AOB is a straight angle?

© State of New South Wales, Department of Education, 2018