Question

Why is 1.618 called a divine ratio or golden ratio?

Answer 1

Two quantities are said to be in golden ratio if the ratio of their sum divided by first term is equal to ratio of first term to second term i.e. $\frac{a+b}{a}=\frac{a}{b}=phi$
This is called a divine ratio as it occurs in nature and it's application in many branches like biology, architecture, geometry of pentagon, decagon and dodecahydron. This ratio contributes to aesthitics and has a great historical significance also.You will find many monuments designed based on this ratio.