Golden Ratio

In mathematics, two quantities are in the golden ratio if their ratio is the same as the ratio of their sum to the larger of the two quantities. Expressed algebraically, for quantities $a$ and $b$ with $a>b>0$

$\frac{a+b}{a}=\frac{a}{b}=:\phi$ where the Greek letter phi ($\phi$ or $\varphi$) represents the golden ratio.

It is an irrational number that is a solution to the quadratic equation $x^2-x-1=0$, with a value of

$\phi =\frac{1+\sqrt{5}}{2}=1.618033988749$