∫｛［sin（x/2）］^（－4）｝dx
＝∫｛1/［sin（x/2）］^4｝dx
＝－∫｛1/［sin（x/2）］^2｝｛－1/［sin（x/2）］^2｝dx
＝－∫｛1＋［cot（x/2）］^2｝d［cot（x/2）］
＝－∫d［cot（x/2）］－∫｛［cot（x/2）］^2｝d［cot（x/2）］
＝－cot（x/2）－（1/3）［cot（x/2）］^3＋C.