Display:

$\nabla^2 (f)=\mathop{\mathrm{div}}(\mathop{\mathrm{grad}}(f))$

Source:

<apply>
     <eq/>
     <apply>
          <laplacian/>
          <ci> f </ci>
     </apply>
     <apply>
          <divergence/>
          <apply>
               <grad/>
               <ci> f </ci>
          </apply>
     </apply>
</apply>