# FreeBSD Manual Pages

```CLOG(3)		       FreeBSD Library Functions Manual		       CLOG(3)

NAME
clog, clogf, and clogl -- complex natural logarithm functions

LIBRARY
Math Library (libm, -lm)

SYNOPSIS
#include <complex.h>

double complex
clog(double complex z);

float complex
clogf(float complex z);

long double complex
clogl(long	double complex z);

DESCRIPTION
The clog(), clogf(), and clogl() functions	compute	the complex natural
logarithm of z.  with a branch cut	along the negative real	axis .

RETURN VALUES
The clog()	function returns the complex natural logarithm value, in the
range of a	strip mathematically unbounded along the real axis and in the
interval [-I* pi ,	+I* pi ] along the imaginary axis.  The	function sat-
isfies the	relationship: clog(conj(z)) = conj(clog(z)).

Argument		  Return value	  Comment
-0	+ I*0		  -infinity +
I*pi			      Divide-by-zero
exception
raised
+0	+ I*0		  -infinity + I*0 Divide by zero exception
raised
x + I*infinity	  +infinity + I*pi/2			      For
finite x
x + I*NaN		  NaN +	I*NaN	  Optionally raises invalid
floating-point exception
for finite x
-infinity + I*y	  +infinity + I*pi			      For
finite
positive-signed
y
+infinity + I*y	  +infinity + I*0 For finite positive-signed y
-infinity + I*infinity		  +infinity + I*3pi/4
+infinity + I*infinity		  +infinity + I*pi/4
+-infinity	+ I*NaN	  +infinity + I*NaN
NaN + I*y		  NaN +	I*NaN	  Optionally raises invalid
floating-point exception
for finite y
NaN + I*infinity	  +infinity + I*NaN
NaN + I*NaN	  NaN +	I*NaN