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Theorem 1

Theorem 2

Theorem 3

Theorem 4

Theorem 5

Theorem 6

Theorem 7

The Seven Theorems

## Angles in a Cyclic Quadrilateral
Fourth circle theorem:
You can use the cursor to move any of points C, D, E or F around the circumference, and hence alter some of the angles. * Hint: Add the pair of angles! Tim Devereux, Created with GeoGebra |