Move the blue hinge to draw any shape.

A pantograph is a mechanical linkage connected in a special manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a second pen. (Wikipedia).[br][br]More than 50 GeoGebra tutorials at [url=http://mathandmultimedia.com/geogebra/]Math and Multimedia[/url]