Example

Consider the divergence of the vector distance $\underline{r}$ from the origin of coordinates to the point $(x,y,z)$. Use of (A.7) yields:

$$\nabla \cdot \underline{r} = \nabla \cdot \left( x \hat{x} + y \hat{y} + z \hat{z} \right)= 3 \space .$$ (2.8)