Some of them are sold, and some of them are free. Many teachers have concerned them. Now, this is a hot theme in Japan, too. According this cencept, we can analyse figure to following procedure. There are some points as independent variables.
Geometrical construction is a function.
Traditionally, locus is a set of points. But, locus in Geometric Constructor is not geometrical object. It is a mere record of motion, but it is treated some data. So, we can observe it clearly and save in files. In the case to investigate that some lines are concurrent or not, we want to zoom in.