## 22 May 2018

### Golden ratio

The golden ratio, also called Phi ($\phi$), is a number which has the following property:

$\phi^2-\phi-1=0$

The only positive solution of this $2$nd degree equation is:

$\phi=\frac{1+\sqrt5}{2}\approx 1.6180339887498948482...$

Golden rectangle

The golden ratio has applications in architecture (eg, the Parthenon in Greece), in painting (eg, by Leonardo Da Vinci, Salvador Dalí and Piet Mondrian), in the dimensions of the books, in music and in the Nature.