Geometric constructions

Abstract

The geometric construction facilities need the least explanation since they parallel what is already done on paper for the most part. However, they often do the job in a somewhat different way since the software has a much more dynamic and flexible medium than paper to work in. For example, a circle through a fixed point with its centre on the cursor may expand or contract on the screen as the cursor is moved: erecting a perpendicular may be done by literally rotating a line through a right angle.