csqrt, csqrtf, csqrtl - complex square root
#include <complex.h>
double complex csqrt(double complex z);
float complex csqrtf(float complex z);
long double complex csqrtl(long double complex z);These functions calculate the complex square root of z, with
a branch cut along the negative real axis. (That means that
csqrt(-1+eps*I) will be close to I while
csqrt(-1-eps*I) will be close to -I, if eps is a small
positive real number.)