DU FIL À LA FIGURE Une approche génétique de la géométrie fondée sur le périmètre comme invariant

Abstract

Teaching perimeter and area often relies on formula application, although students may find it difficult to distinguish these two quantities. This paper proposes using an inextensible string of fixed length to construct and compare plane figures. Perimeter is treated as the invariant, shape as the variable, and area as a quantity depending on the configuration. The paper outlines the didactic rationale, selected mathematical relations, a proposed five-session sequence for lower secondary school, and an evaluation protocol. The sequence has not yet been tested; its effects on learning therefore remain to be established.