golden mean

Golden Mean
Golden Ratio

The number , or about 1.61803. The Golden Mean arises in many settings, particularly in connection with the Fibonacci sequence. Note: The reciprocal of the Golden Mean is about 0.61803, so the Golden Mean equals its reciprocal plus one. It is also a root of x2 – x – 1 = 0.

Note: The Greek letter phi, φ, is often used as a symbol for the Golden Mean. Occasionally the Greek letter tau, τ, is used as well.