double _Complex cacos(double _Complex z)
{
 z = casin(z);
 return ((union { _Complex double __z; double __xy[2]; }){.__xy = {(1.57079632679489661923 - ((double)(z))),(-((union { _Complex double __z; double __xy[2]; }){(_Complex double)(z)}.__xy[1]))}}.__z);
}