From teaching experience. VI. Symmetry of borders
The article shows that consideration of 7 symmetry groups of borders in a university course in crystallography is advisable for a number of reasons. On their example, the simplest symmetry groups of infinite figures are easily constructed. The theorem on the compositions of planes and axes of symmetry with orthogonal translations generating homogeneous symmetry elements is clearly explained. An analysis of the symmetry groups of borders in nature and urban landscapes (fences, lattices, ornaments, mosaics, etc .) address students to the fundamental problem of the prevalence of 230 space symmetry groups in the mineral world.