From Here vec$(grad)\frac{1}{|(vec(r))-\text{v}\text{e}\text{c}(r{)}^{\text{'}}|}=-$vec$(grad)\frac{1}{|(vec(r))-(vec(r))|}$ prove that we con write the equation of potential of dipole leger is $(vec(r))=\frac{-1}{4{}_0}{\displaystyle \underset{s^{\text{'}}}{\overset{\phantom{}}{}}}$vec$(D)(vec(r{)}^{\text{'}})d$ Where $d=\frac{-cos}{{}^2}da$