1. Introduction

The locus is defined and correlated with the notions of generated trajectories and curves. It is considered a geometric Figure in which one side becomes fixed, and the others are moving, so that certain specified points describe the trajectories, i.e. curves assimilated to geometric places, such as conical curves: ellipse, parabola, hyperbola. Drawing these curves starting from geometric problems is easy by using the Theory of Mechanisms. The equivalent mechanisms are built and analyzed. For those who are not familiar with the Theory of Mechanisms, the strictly necessary elements are given in order to be able to construct the equivalent mechanisms and then to determine the trajectories of some points. The diagrams of the kinematic elements with rotational motion R, and translational motion (sliding), P are indicated, showing how the elements can be connected, also the cases when the lengths of some elements are equal to zero are presented too. The method of contours developed by Tchebichev is shown and examples of mechanisms and generated curves are given [1, 2, 3] (Cebâşev in Izobrannâe trud, Izd, Nauka, Moskva, 1953; Popescu in Mecanisme, vol. I, II. Tipografia Universităţii din Craiova, 1995; Popescu in Proiectarea mecanismelor plane, Craiova, Editura Scrisul Românesc, 1977).