use the polar form of the complex number to find a value in Cartesian form, z = x + iy.
sqrt(-i)
\(z = r e^{i \theta}\\ \sqrt{z} = \sqrt{r} e^{i \theta/2}\\ -i = 1\cdot e^{-i \pi /2}\\ \sqrt{-i} = \sqrt{1} e^{-i \pi/4} = e^{-i\pi/4} = \\ \cos(-\pi/4) + i \sin(-\pi/4) = \\ \dfrac{\sqrt{2}}{2}(1 - i)\)
Thanks :D. Really helpful. I didn't realize that you should sqrt the equation to find out the equation for a rooted complex number :D