0\\
(x+iy)^2+\sqrt{x^2+y^2}=0\\
x=0\\
y=-1\\\\
z=-i\\\\
r=\sqrt{1^2}=1\\
\phi=arccos(0) = \frac{\pi}{2}" alt="z^2=(x+iy)^2\\
|z|=\sqrt{x^2+y^2}\\\\
z^2>0\\
(x+iy)^2+\sqrt{x^2+y^2}=0\\
x=0\\
y=-1\\\\
z=-i\\\\
r=\sqrt{1^2}=1\\
\phi=arccos(0) = \frac{\pi}{2}" align="absmiddle" class="latex-formula">