How can you construct an equilateral triangle with the 3 vertices lying on 3 parallel lines?

Click the ">>" button below to see the construction.

Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and active in your browser (Click here to install Java now)

How can you prove that ΔABC constructed above is equilateral? Click here to see the proof.

Education Infrastructure Division, Education Bureau, HKSARG. Created with GeoGebra