This could also be written as

`del/(delx)[(delF)/(dely)]`

This expression means

Find the partial derivative with respect to

xof the partial derivative with respect toy.

In our example above, *F*(*x,y*) = *y* + 6 sin *x* + 5*y*^{2}, we found

`(delF)/(dely)=1+10y`

To find `(del^2F)/(delxdely)`, we need to find the partial derivative with respect to *x* of `(delF)/(dely)`.

`(del^2F)/(delxdely)=del/(delx)[(delF)/(dely)]`

`=del/(delx)[1+10y]`

`=0`

Since *y* is a constant (when we are considering differentiation with respect to *x*), its derivative is just 0.