Given a rectangle having sides in the ratio , is defined as the unique number such that partitioning the original rectangle into a square and newrectangle as illustrated above results in a new rectangle which also has sides in the ratio (i.e., such that the yellow rectangles shown above are similar). Such a rectangle is called a golden rectangle, and successive points dividing a golden rectangle into squares lie on a logarithmic spiral, giving a figure known as a whirling square.