Equation   = 0  has three complex solutions, that are the roots of degree 3 of 8:


            trigonometric form             complex number form  
            r*(cos(t) + i*sin(t))          a + bi


1)  z = 2 = 2*(cos(0°)   + i*sin(0°)    =  2 + i*0;



2)  z =     2*(cos(120°) + i*sin(120°)) =  2*((-1/2) + i*(sqrt(3)/2)}}} = -1 + i*sqrt(3);



3)  z =     2*(cos(240°) + i*sin(240°)) =  2*((-1/2) - i*(sqrt(3)/2)}}} = -1 - i*sqrt(3);