The Golden Mean or Ratio[(1+sqrt(5))/2‪]‬

The golden ratio, also known as the divine proportion, golden mean, or golden section, is a number often encountered when taking the ratios of distances in simple geometric figures such as the pentagon, pentagram, decagon and dodecahedron. It is denoted phi, or sometimes tau.


The designations "phi" (for the golden ratio conjugate 1/phi) and "Phi" (for the larger quantity phi) are sometimes also used (Knott), although this usage is not necessarily recommended.