Silva Kmetič, Zavod RS za šolstvo, Tomaž Miholič, Osnovna šola Duplek, Vinko Zobec, Osnovna šola Poljčane

The plan of instructions for the development of the concept of altitude of a triangle in elementary school we completed content objectives from the national curriculum with the general objective of teaching mathematics: a student develops mathematical thinking. The additional steps of dynamic schematisation should be taxonomic enrichment of expected students’ achievements in terms of use, understanding the concept and in terms of understanding the mathematical definition. The concept development was planned according to van Hiele scheme, which was supplemented with dynamic schematization. The activities with concrete models were intertwined with constructions using geometrical tools on paper (results are static images, symbolic and verbal descriptions), and with exploring a position of an altitude in dynamic changeable triangles. We observed the process of learning and measure progress of students’ knowledge. When observing learning, in addition to already known problems such as the uncertainty of the construction of altitude in a given triangle, depending on a type of triangle and depending on position of the triangle base with respect to the edge of the work surface (sheet), we have noticed also other less familiar misconceptions. The achievement on final testing would be hardly related just to the use of dynamic schematization, because it is a shared result of all carefully planned learning steps. We particularly tested and analyzed qualitatively students ‘dynamic’ view of the geometry in relation the topic. The result points to a necessary new learning step, which would develop the concepts of dependent and independent geometric objects in the use of dynamic geometry program.