Hi, If I remember well someone on the list made yingyang like at riotorto. Could you do the same with this triskell ? http://hgng.free.fr/2/yinyangyung.JPG That Lohmueller friedrich made for me I need the equation which do it in sage and maxima. thanks Kind regards Henri (It's a humble wish ... But I know they are lot of good soul in this list...)