The number = (1 + 5)/2 = 1.618 ..., or more strictly /1, is called the golden ratio. A rectangle which has its sides in the ratio /1 is called a golden rectangle. If a golden rectangle with sides and 1 has a 1 x 1 square removed then the remaining smaller rectangle is also a golden rectangle. The ancient Greeks believed that the golden rectangle has proportions which are pleasing to the eye. Close approximations to such rectangles occur in many of their buildings such as the Parthenon in Athens, although some scholars dispute the connection.
= (1 + 
5)/2 = 1.618 ..., or more strictly 
