Coordinate cartesiane ortogonali

$$\begin{array}{rcl} \nabla^2\ \vec{V} & = & \left(\ensuremath... ...nsuremath{\frac{\partial^2 w}{\partial z^2}}\right) \end{array}$$

$$\nabla^2 \ \vec{V}\ =\ \vec{\imath}\ \nabla^2(u)\ +\ \vec{\jmath}\ \nabla^2(v) \ +\ \vec{k}\ \nabla^2(w)$$