How to plot the boundary of the corresponding convex cone in MATLAB

Question

The special set of $n\times n$ real symmetric positive semidefinite matrices, denoted by + is called a convex cone. Consider the special case +2. For a symmetric matrix $\begin{bmatrix} x & y \\ y & z \end{bmatrix}$ the conditions $y^2>xz$ and $x+z \ge 0$ makes $A$ to positive semi-definite matrix. Plot the boundary of the corresponding convex cone, i.e., $y^2=xz$ where $x\ge 0$ and $z\ge 0$ in − in MATLAB. NOTE: You can use ([45 45 10]) command to adjust azimuth, elevation and skew of the plot, respectively. Does anybody know how can ı code this in MATLAB?