Islamic Design

38 39 between the two families Decimal Connections The basic tenfold patterns on the previous pages can also be generated from a subgrid of regular decagons, pentagons and pentagonbased hexagons below left. Placing pentagons and pentagram stars in this subgrid gives the two patterns below right. Arranging the two patterns this way suggests the possibility of varying the angles formed where paths cross at the subgrids edge midpoints. The Umm alGirih has angles of 108 at these fixed points, while the other basic tenfold pattern has angles of 36. A surprisingly floral design is given by 90 top left, while 72 generates a pattern combining both families of tenfold forms, an example of how successfully they can be integrated top right. Finally, an angle of 54 produces particularly elegant petal shapes and a small central star the same shape as the first examples central star bottom left. The final example opposite takes the second variation dotted line and replaces its rosettes with those found on the previous page, showing just how beautifully harmonious the interrelationships between patterns in these tenfold formlanguages can be.