hypot man page
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():
_ISOC99_SOURCE  _POSIX_C_SOURCE >= 200112L
 _XOPEN_SOURCE
 /* Since glibc 2.19: */ _DEFAULT_SOURCE
 /* Glibc versions <= 2.19: */ _BSD_SOURCE  _SVID_SOURCE
hypotf(), hypotl():
_ISOC99_SOURCE  _POSIX_C_SOURCE >= 200112L
 /* Since glibc 2.19: */ _DEFAULT_SOURCE
 /* Glibc versions <= 2.19: */ _BSD_SOURCE  _SVID_SOURCE
Description
These functions return sqrt(x*x+y*y). This is the length of the hypotenuse of a rightangled 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 rightangled 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 floatingpoint exception (FE_OVERFLOW) is raised.
 Range error: result underflow

An underflow floatingpoint exception (FE_UNDERFLOW) is raised.
These functions do not set errno for this case.
Attributes
For an explanation of the terms used in this section, see attributes(7).
Interface  Attribute  Value 

hypot(), hypotf(), hypotl()  Thread safety  MTSafe 
Conforming to
C99, POSIX.12001, POSIX.12008.
The variant returning double also conforms to SVr4, 4.3BSD.
See Also
Colophon
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Referenced By
The man pages hypotf(3) and hypotl(3) are aliases of hypot(3).