By magic, my previous posting evaporated !
1. irregular, regular [various constructions]
2. star 5/2 maths
3. Holly star

Maths Polygon Area_Perimeter.sm (33,38 KiB) scaricato 1323 volta(e).
Maths Polygon Star 5_2.sm (965,24 KiB) scaricato 1380 volta(e).