How to "rotate the phase"?
Ok I give the answer by myself, but it’s only half of answer. As I know we can rotate $ 90^o $ the phase by multiplying the wave by $ j $ - imaginary number. And to rotate it to $ 180^o $ we need multiply by $ j^2 $ (or just $ -1 $ which is the same). To rotate $ 270^o $ we need to multiply by $ j^3 $, and so on...

But if we want rotate something between? For example $ 45 ^o $ or $ 30^o $. What we need to multiply by?