根轨迹的渐近线：当开环有限极点数\(n\)大于有限零点数\(m\)时，有\(n-m\)条根轨迹分支沿着与实轴交角为\(\varphi_a\)、交点为\(\sigma_a\)的一组渐近线趋向无穷远处，且有

\(\displaystyle\varphi_u=\frac{(2 k+1) \pi}{n-m} ; \quad k=0,1,2, \cdots, n-m-1\)

和

\(\sigma_a=\frac{\displaystyle\sum_{i=1}^n p_i-\sum_{j=1}^m z_j}{n-m}\)