# Definition:Golden Mean/One Minus Golden Mean

## Definition

Let $\phi$ denote the golden mean:

$\phi = \dfrac {1 + \sqrt 5} 2$

The number:

$1 - \phi$

is often denoted $\hat \phi$.

### Decimal Expansion

The decimal expansion of $\hat \phi$, $1$ minus the golden mean, starts:

$\hat \phi \approx -0 \cdotp 61803 \, 39887 \ldots$

## Also denoted as

The number $1 - \phi$ can also be seen denoted as $\phi'$.