phase | Function |

**Syntax****phase**number → phase**Arguments and Values**`number`— a*number*.`phase`— a*number*.**Description****phase**returns the phase of`number`(the angle part of its polar representation) in radians, in the range −π (exclusive) if minus zero is not supported, or −π (inclusive) if minus zero is supported, to π (inclusive). The phase of a positive*real*number is zero; that of a negative*real*number is π. The phase of zero is defined to be zero.If

`number`is a*complex float*, the result is a*float*of the same*type*as the components of`number`. If`number`is a*float*, the result is a*float*of the same*type*. If`number`is a*rational*or a*complex rational*, the result is a*single float*.The branch cut for

**phase**lies along the negative real axis, continuous with quadrant II. The range consists of that portion of the real axis between −π (exclusive) and π (inclusive).The mathematical definition of

**phase**is as follows:`(phase`

) = (atan (imagpart*x*) (realpart*x*))*x***Examples**(phase 1) → 0.0s0 (phase 0) → 0.0s0 (phase (cis 30)) → -1.4159266 (phase #c(0 1)) → 1.5707964

**Exceptional Situations**Should signal

**type-error**if its argument is not a*number*. Might signal**arithmetic-error**.**See Also**