Shape

328 III Using It to Design
I seem to be stuck. But no, this isn’t the end of it—I can do much more with my schemas
to get exactly the results I want. Look at it another way and see how it works. The
diagonal of a quadrilateral forms twin triangles
and it’s the same for a pentagon with a concavity, at least in the special case where a
diagonal and an edge are collinear
Shapes are always ambiguous, and the ambiguity is something to use. It seems that I
already know how to go on. If I apply the inverse of my division schema x fi divðxÞ,
that is to say, the schema
divðxÞ fi x
I can erase diagonals in polygons in just the right way. For quadrilaterals in the palmleaf
umbrella, I need the rule
and this one
and for the pentagon, the rule
is fine. Inverses often come in handy—the schema x fi bðxÞ determines the boundary
of a shape with lines, planes, or solids, while its inverse bðxÞ fi x works to color regions
in my designs. And then there’s the palm-leaf umbrella