$\left\{\begin{matrix}c=\frac{y}{7xs^{2}\cos(7x)}\text{, }&s\neq 0\text{ and }\nexists n_{1}\in \mathrm{Z}\text{ : }x=\frac{\pi n_{1}}{7}+\frac{\pi }{14}\text{ and }x\neq 0\\c\in \mathrm{C}\text{, }&\left(x=0\text{ or }\exists n_{1}\in \mathrm{Z}\text{ : }x=\frac{\pi n_{1}}{7}+\frac{\pi }{14}\text{ or }s=0\right)\text{ and }y=0\end{matrix}\right.$

$\left\{\begin{matrix}s=-\frac{\sqrt{7}c^{-\frac{1}{2}}x^{-\frac{1}{2}}\sqrt{y}\left(\cos(7x)\right)^{-\frac{1}{2}}}{7}\text{; }s=\frac{\sqrt{7}c^{-\frac{1}{2}}x^{-\frac{1}{2}}\sqrt{y}\left(\cos(7x)\right)^{-\frac{1}{2}}}{7}\text{, }&c\neq 0\text{ and }\nexists n_{1}\in \mathrm{Z}\text{ : }x=\frac{\pi n_{1}}{7}+\frac{\pi }{14}\text{ and }x\neq 0\\s\in \mathrm{C}\text{, }&\left(x=0\text{ or }\exists n_{1}\in \mathrm{Z}\text{ : }x=\frac{\pi n_{1}}{7}+\frac{\pi }{14}\text{ or }c=0\right)\text{ and }y=0\end{matrix}\right.$