2017-09-15

Aliases: clogf(3), clogf(3), clogf(3), clogf(3), clogf(3), clogf(3), clogl(3), clogl(3), clogl(3), clogl(3), clogl(3), clogl(3)

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### man-pages

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## NAME

clog, clogf, clogl - natural logarithm of a complex number

## SYNOPSIS

**#include <complex.h>**

**double complex clog(double complex**

*z*

**);**

**float complex clogf(float complex**

*z*

**);**

**long double complex clogl(long double complex**

*z*

**);**

Link with

*-lm*.## DESCRIPTION

These functions calculate the complex natural logarithm of

*z*, with a branch cut along the negative real axis.The logarithm

**clog**() is the inverse function of the exponential cexp(3). Thus, if*y = clog(z)*, then*z = cexp(y)*. The imaginary part of*y*is chosen in the interval [-pi,pi].One has:

clog(z) = log(cabs(z)) + I * carg(z)

Note that

*z*close to zero will cause an overflow.## VERSIONS

These functions first appeared in glibc in version 2.1.

## ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface |
Attribute |
Value |

Thread safety | MT-Safe |

## CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.

## SEE ALSO

## COLOPHON

This page is part of release 5.00 of the Linux

*man-pages*project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.