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Javascript Version

An Isosceles Triangle Theorem

In the figure, ABD is an isosceles triangle with AB = BD. Also AE = CD.

F is the intersection of AD and EC.

The theorem states that EF = FC.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

We also see the ratio of AF / FD. Can you come up with a formula for this ratio in terms of AB, AD and AE?

If you are interested in this applet, you may like our Interactive Symbolic Geometry software Geometry Expressions.