If I show, that w = 4(pi)n works for all z (n an integer), then I do not find all such w that do this, for all z in C, because 2(pi), works also, but is not in the set 4(pi)n , n an integer. So, if I would claim that all w=4(pi)n works for all z, this is true, but, I do not find all such w.