sqrt (3)
Leading comments
Copyright 1993 David Metcalfe (david@prism.demon.co.uk) and Copyright 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpages@gmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting ...
NAME
sqrt, sqrtf, sqrtl  square root functionSYNOPSIS
#include <math.h> double sqrt(double x);
float sqrtf(float x);
long double sqrtl(long double x);
Link with lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sqrtf(), sqrtl():

_BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 600  _ISOC99_SOURCE 
_POSIX_C_SOURCE >= 200112L;
or cc std=c99
DESCRIPTION
These functions return the nonnegative square root of x.RETURN VALUE
On success, these functions return the square root of x.If x is a NaN, a NaN is returned.
If x is +0 (0), +0 (0) is returned.
If x is positive infinity, positive infinity is returned.
If x is less than 0, a domain error occurs, and a NaN is returned.
ERRORS
See math_error(7) for information on how to determine whether an error has occurred when calling these functions.The following errors can occur:
 Domain error: x less than 0
 errno is set to EDOM. An invalid floatingpoint exception (FE_INVALID) is raised.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).Interface  Attribute  Value 
sqrt(), sqrtf(), sqrtl()  Thread safety  MTSafe 
CONFORMING TO
C99, POSIX.12001, POSIX.12008.The variant returning double also conforms to SVr4, 4.3BSD, C89.