\[\begin{equation} \vec{p_{4N}}= \left[ \begin{array}{cc} \sum_{k=1}^N\left\{L\left(\cos\alpha_{2k-1}+\cos\alpha_{2k}\right)+h_1\cos\beta_{2k-1}+h_2\cos\beta_{2k}\right\}\\ \sum_{k=1}^N\left\{L\left(\sin\alpha_{2k-1}+\sin\alpha_{2k}\right)+h_1\sin\beta_{2k-1}+h_2\sin\beta_{2k}\right\}\\ \end{array} \right] \end{equation}\]
In case of all modules are same and \(L>>h_1,h_2 \)\(\phi\) can be calculated from (15),