8. Convert the parametric equations $\left\{\begin{array}{l}x=\frac{\cos \theta}{1+\cos \theta} \\ y=\frac{\sin \theta}{1+\cos \theta}\end{array}\right.$ to a Cartesian equation is $\qquad$ .
8. $y^{2}=-2\left(x-\frac{1}{2}\right)$ Hint: You can express $\sin \theta, \cos \theta$ in terms of $x, y$, and then use the square relationship to eliminate $\theta$.