The concept of “golden ratio” can be traced back to ancient Greek. Its definition is based on the way that a rod is cut a rod into two pieces, the ratio between the length of two pieces is the same as the ratio between the length of the longer one over that of initial rod
Consider the image above, with the initial rod of length 1 and it is cut at . Then the value of (or ) corresponds to golden ratio when , which gives and . Either of those value can be considered the “golden ratio”, depending on personal taste.
Note that , which is the point of this article.
The other value, , which can explain the ratio of national flags is mostly 2/3.