$\left\{\begin{matrix}R=\frac{W^{2}+d^{2}}{2d}\text{, }&d\neq 0\text{ and }arg(\frac{W^{2}}{2d}-\frac{d}{2})<\pi \\R\in \mathrm{C}\text{, }&d=0\text{ and }W=0\text{ and }arg(R)<\pi \\R=d\text{, }&d=-W\text{ or }d=W\end{matrix}\right.$

$W=-\sqrt{d}\sqrt{2R-d}$
$W=\sqrt{d}\sqrt{2R-d}\text{, }R=d\text{ or }arg(R-d)<\pi $

$\left\{\begin{matrix}R=\frac{W^{2}+d^{2}}{2d}\text{, }&\left(d\leq -|W|\text{ and }d<0\right)\text{ or }\left(d>0\text{ and }d\leq |W|\right)\\R\geq 0\text{, }&d=0\text{ and }W=0\end{matrix}\right.$