SQRT(3) Linux Programmer's Manual SQRT(3)
sqrt - square root function
#include <math.h> double sqrt(double x);
The sqrt() function returns the non-negative square root of x. It fails and sets errno to EDOM, if x is negative.
EDOM x is negative.
SVID 3, POSIX, BSD 4.3, ISO 9899
hypot(3) June 21, 1993 1