This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

hypot(x,y), hypot(y,x), and hypot(x, -y) are equivalent.

       hypot(x, ±0) is equivalent to fabs(x).

       Underflow only happens when both x and y are subnormal and the (inexact) result is also subnormal.

       These functions take precautions against overflow during intermediate steps of the computation.

       On error, the expressions (math_errhandling & MATH_ERRNO) and  (math_errhandling  &  MATH_ERREXCEPT)  are
       independent of each other, but at least one of them must be non-zero.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical  and  Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE  and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                         HYPOT(3POSIX)

       The  functionality  described  on  this  reference  page is aligned with the ISO C standard. Any conflict
       between the requirements described  here  and  the  ISO C  standard  is  unintentional.  This  volume  of
       POSIX.1‐2017 defers to the ISO C standard.

       These functions shall compute the value of the square root of x2+y2 without undue overflow or underflow.

       An   application   wishing   to   check   for  error  situations  should  set  errno  to  zero  and  call
       feclearexcept(FE_ALL_EXCEPT) before  calling  these  functions.  On  return,  if  errno  is  non-zero  or
       fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

       These functions shall fail if:

       Range Error The result overflows.

                   If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then  errno  shall  be
                   set  to [ERANGE].  If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
                   then the overflow floating-point exception shall be raised.

       These functions may fail if:

       Range Error The result underflows.

                   If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then  errno  shall  be
                   set  to [ERANGE].  If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
                   then the underflow floating-point exception shall be raised.

       Thefollowingsectionsareinformative.

       See the EXAMPLES section in atan2().

       None.

       hypot, hypotf, hypotl — Euclidean distance function

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       None.

       Upon  successful  completion, these functions shall return the length of the hypotenuse of a right-angled
       triangle with sides of length x and y.

       If the correct value would cause overflow, a range error shall occur and hypot(), hypotf(), and  hypotl()
       shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.

       If x or y is ±Inf, +Inf shall be returned (even if one of x or y is NaN).

       If x or y is NaN, and the other is not ±Inf, a NaN shall be returned.

       If  both  arguments  are  subnormal  and the correct result is subnormal, a range error may occur and the
       correct result shall be returned.

atan2(), feclearexcept(), fetestexcept(), isnan(), sqrt()

       The Base Definitions volume of POSIX.1‐2017, Section4.20, TreatmentofErrorConditionsforMathematicalFunctions, <math.h>

       #include <math.h>

       double hypot(double x, double y);
       float hypotf(float x, float y);
       long double hypotl(long double x, long double y);