The Surfer's Board - Fashioned of Aether and Double and Triple Integrals and a Fantastic (4) for Stability

 

$$\iint_D g(u,v) \left\| \mathbf{r}_u \times \mathbf{r}_v \right\| \, du \, dv$$

$$\int_0^{2\pi} \int_0^a \int_0^{f(r,\theta)} r \, dz \, dr \, d\theta$$

4