0. Test

:
 arg(z) > pi/4; t,0; t,t
 arg(z) > 3*pi/4 or arg(z) < -pi/2; 0,t; t,-t
:
 abs(arg(z)) <> arg(2+i); 2*t,-t; 2*t,t
 arg(z) <> arg(1+-2*i); t,0; t,-2*t; t,2*t
