Fourth circle theorem

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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:

What's the connection between pairs of opposite angles (α and γ or β and δ)? *

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.
You can also move point A or B to change the size of the circle.

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* Hint: Add the pair of angles!
If you need them, the seven circle theorems here

Tim Devereux, Created with GeoGebra

Fourth circle theorem

Home First page Theorem 1 Theorem 2 Theorem 3 Theorem 4 Theorem 5 Theorem 6 Theorem 7 The Seven Theorems

Angles in a Cyclic Quadrilateral

Home
First page
Theorem 1
Theorem 2
Theorem 3
Theorem 4
Theorem 5
Theorem 6
Theorem 7
The Seven Theorems