N e m n ( k , r ) = z n ( ρ ρ ) ρ ρ cos ⁡ ⁡ ( m φ φ ) n ( n + 1 ) P n m ( cos ⁡ ⁡ ( θ θ ) ) e r + cos ⁡ ⁡ ( m φ φ ) d P n m ( cos ⁡ ⁡ ( θ θ ) ) d θ θ 1 ρ ρ d d ρ ρ [ ρ ρ z n ( ρ ρ ) ] e θ θ − − m sin ⁡ ⁡ ( m φ φ ) P n m ( cos ⁡ ⁡ ( θ θ ) ) sin ⁡ ⁡ ( θ θ ) 1 ρ ρ d d ρ ρ [ ρ ρ z n ( ρ ρ ) ] e φ φ