Based on the period development of number 1/7 and its addition property, so called 1/7 ellipsea in 2D and 3D are defined as well as 1/7 butterfly wings in 2D and 3D and 1/7 rosetas in 2D and 3D. The deduction of these shapes is a suitable task for secondary school pupils for their independent investigation.
The article is accompanied by tables and pictures.