A Synthetic Method for Representation of Quadric Axes

This paper describes a synthetic method to construct principal axes starting from any given portion of a quadric surface. This problem, which belongs to classical problems of descriptive geometry, is particularly complex if faced with graphical representation methods, that is why there are few studies about it. Transposition into space through digital representation has allowed us to develop a simple and rigorous solution to that problem, first verified in the cones case, then extended to all quadrics. The review in space of classical problems of descriptive geometry allowed also to rework and represent a theoretical solution of the same problem, given by Otto Wilhelm Fiedler in the second half of the nineteenth century