Planimetric Warm-ups for Developing Geometric Thinking.

Solving problems in geometry, whether planar or spatial, is for students generally more difficult than solving problems in other branches of mathematics, e.g. in arithmetic or in algebra. Therefore, it is necessary to consider how students’ geometric thinking and spatial imagination can be practised and developed. One of the options is to provide students with appropriate examples that would practise and develop their geometric thinking and spatial imagination in a relatively short time. Such examples we can denote "warm-ups". There are organized the preparatory courses for students of the Faculty of mechanical engineering by our department before the first semester of their bachelor study starts. Practising geometry is one part of the preparatory course. The inclusion of the planimetric warm-ups in one lesson of the preparatory course seems to be useful. There are mentioned several planimetric warm-ups drawn in software GeoGebra, creating the base of so-called online GeoGebra book named Planimetric Warm-ups that is used as e-learning material during the preparatory course, in this contribution. [ABSTRACT FROM AUTHOR]