# PHI

## Purpose:

Macro. Returns *φ,* the "golden mean" or
"golden ratio".

## Syntax:

PHI

## Expansion:

1.61803398874989484820

## Remarks:

This constant can
be derived by solving the following set of equations:

if |
a/b =
b/(a +
b) |

and |
a =
1 |

then |
b =
φ |

PHI is the positive root of the polynomial
*x*^{2}
- x - 1.

PHI is particularly useful if you happen
to be an ancient Greek.

## See Also:

ACSCH

DEG

GAMM

INF

LN

PI

POLYROOT

ROOTS