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Linux 2.6 - man page for hypotl (linux section 3)

HYPOT(3)						     Linux Programmer's Manual							  HYPOT(3)

NAME
hypot, hypotf, hypotl - Euclidean distance function
SYNOPSIS
#include <math.h> double hypot(double x, double y); float hypotf(float x, float y); long double hypotl(long double x, long double y); Link with -lm. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): hypot(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc -std=c99 hypotf(), hypotl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc -std=c99
DESCRIPTION
The hypot() function returns sqrt(x*x+y*y). This is the length of the hypotenuse of a right-angled triangle with sides of length x and y, or the distance of the point (x,y) from the origin. The calculation is performed without undue overflow or underflow during the intermediate steps of the calculation.
RETURN VALUE
On success, these functions return the length of a right-angled triangle with sides of length x and y. If x or y is an infinity, positive infinity is returned. If x or y is a NaN, and the other argument is not an infinity, a NaN is returned. If the result overflows, a range error occurs, and the functions return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively. If both arguments are subnormal, and the result is subnormal, a range error occurs, and the correct result 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: Range error: result overflow errno is set to ERANGE. An overflow floating-point exception (FE_OVERFLOW) is raised. Range error: result underflow An underflow floating-point exception (FE_UNDERFLOW) is raised. These functions do not set errno for this case.
CONFORMING TO
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD.
SEE ALSO
cabs(3), sqrt(3)
COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2010-09-20 HYPOT(3)