9. Given the parabola $C: x^{2}=2 p y(p>0)$, draw two tangent lines $R A$ and $R B$ from the point $R(1,-1)$ to the parabola $C$, with the points of tangency being $A$ and $B$. Find the minimum value of the area of $\triangle R A B$ as $p$ varies.
9. Analysis: It is easy to know that the equation of the chord of tangents $A B$ corresponding to $R$ is: $p y-x-p=0$. By combining the line $A B$ with the parabola equation, we get: $x^{2}-2 x-2 p=0$. By Vieta's formulas: $x_{A}+x_{B}=2, x_{A} \cdot x_{B}=-2 p$, hence we know $S_{\mathrm{VR} A B}=\frac{|1+2 p| \cdot\left|x_{A}-x_{B}\right|}{2}=\frac{|1+2 p| \cdot \sqrt{1+2 p}}{p} \geq 3 \sqrt{3}$