What is the formula for golden ratio

a + b is to a as a is to b

Step-by-step explanation:

The Golden ratio is a special number found by dividing a line into two parts so that the longer part divided by the smaller part is also equal to the whole length divided by the longer part. It is often symbolized using phi, after the 21st letter of the Greek alphabet.

The formula for the golden ratio is (1 + the square root of 5) / 2