Fifth circle theorem

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

Tangent lengths

Fifth circle theorem:

What can you say about the lengths of the two tangents CD and CE?

You can use the cursor to move point C, and you can change the size of the circle by moving point A or B.

This is a Java Applet created using GeoGebra from - it looks like you don't have Java installed, please go to

If you need them, the seven circle theorems here

Tim Devereux, Created with GeoGebra