Fuente TeX:

=\frac{\sqrt{2}}{2} \int_{1}^{2} \int_{0}^{2\pi} \rho (\rho \cos{(\theta)}, \rho \sin{(\theta)}, (\rho-2)(\rho-1))\cdot \left(\cos{(\theta)},\sin{(\theta)},-1\right) dS