摘要：Regular, semi-regular and polygons with right angles are constructed in Cayley-Klein’s model of the projectively extended hyperbolic plane (H-plane). Some of the construction are analogous with the Euclidean ones. The ones for which there are not Euclidean analogues are carried out in original way characteristic for a H-plane. The construction of the defect of an equilateral triangle is of a special inte- rest having the construction of the regular heptagon as its consequence.
