The Golden Ratio

Although not naming it the Golden Ratio, around 300 BCE Euclid of Alexandria defined the proportion: "A straight line is said to have been cut into extreme and mean ratio when, as the whole line is to the greater segment, so is the greater to the lesser.
" The precise value of the Golden Ratio is an irrational number, phi (1.61803399...), and, like the irrational number pi (3.14159265...) or e (2.71828183...), was considered by the Pythagoreans to be so horrific that its knowledge should be kept secret.