You can explore all the circle theorems with Tim Devereux’s GeoGebra applets. You can access each theorem from the menu on the left which includes a useful summary of all the theorems.
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Study some proofs: circle theorems – some proofs
Mathematics for Students 
Hi,
The link to my GeoGebra Applets page is now a php file – http://www.timdevereux.co.uk/maths/geompages/index.php
Best wishes
Tim Devereux
Thank you so much Tim, all links above now corrected. These applets are great – both for demonstrating in class and for students self-study.