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 {\displaystyle a} and b {\displaystyle b} with a > b > 0 {\displaystyle a>b>0} , a {\displaystyle a} is in a golden ratio to b {\displaystyle b} if a + b a = a b = φ , {\displaystyle {\frac {a+b}{a}}={\frac {a}{b}}=\varphi ,} where the Greek letter phi ( φ {\displaystyle \varphi } or ϕ {\displaystyle \phi } , or Φ {\displaystyle \Phi } ) denotes the golden ratio.