Eugenio Roanes Macias & Eugenio Roanes Lozano Automated Search for Geometric Loci Looking for geometric loci is easier using suitable computer systems. A Dynamic Geometry System can help in a first exploration of the problem and a Computer Algebra System is necessary to use algebraic methods of mechanical proving. How to use the last one in the discovering process and how to proof theorems relative to geometric loci in a automatic way is described. Two examples are shown as illustration: the extension of Simson's theorem (discovered last century by Jakob Steiner) and a second extension (recently found by Professor Miguel de Guzman).