Example 5 (p. 734)
> F := [ x^2*y*z, 3*x*y*z^3, x^2-z^2 ];
> diverge( F, [x,y,z] );
> curl( F, [x,y,z] );
>
![F := [x^2*y*z, 3*x*y*z^3, x^2-z^2]](images/sec17-111.gif){kind=small}
![VECTOR([-9*x*y*z^2, x^2*y-2*x, 3*y*z^3-x^2*z])](images/sec17-113.gif){kind=small}