form inertia (field w, trial u, test v,
  quadrature_option_type qopt = quadrature_option_type())
{
  return
    integrate (- dot(trans(grad_h(v))*w,u) - 0.5*div_h(v)*dot(u,w), qopt)
  + integrate ("internal_sides",
           dot(average(u),normal())*dot(jump(v),average(w))
     + 0.5*dot(jump(v),normal())
           *(dot(average(u),average(w)) + 0.25*dot(jump(u),jump(w))), qopt)
  + integrate ("boundary", 0.5*dot(v,normal())*dot(u,w), qopt);
}
field inertia_fix_rhs (test v, 
  quadrature_option_type qopt = quadrature_option_type())
{
  return integrate("boundary", -dot(g(),normal())*dot(g(),v), qopt);
}

