Formula
$$\sqrt[n]z=\sqrt[n]{r(\cos\psi+i\sin\psi)} = \sqrt[n]r \left(\cos\dfrac{\psi+2\pi k}{n} + \sin\dfrac{\psi+2\pi k}{n} \right) \\[1.2 em] k=0,1,2,\dots,n-1$$
$$\sqrt[n]z=\sqrt[n]{r(\cos\psi+i\sin\psi)} = \sqrt[n]r \left(\cos\dfrac{\psi+2\pi k}{n} + \sin\dfrac{\psi+2\pi k}{n} \right) \\[1.2 em] k=0,1,2,\dots,n-1$$