\[h_{2s}(\theta,\alpha)=\frac{e^{i\alpha(\pi-\theta)}}{1+e^{-i\theta}}a_{2s}(%
\theta,\alpha)+(-1)^{s-1}i\frac{1\cdot 3\cdot 5\cdot\cdot\cdot(2s-1)}{(c(%
\theta))^{2s+1}},\]