Rule #9 The gain at a selected point SI on the locus (在某特定点上的根轨迹增益K) Rule#10 The sum of the closed- loop poles(闭环极点 之和) Rule #l The number of branches of the root locus (根轨迹的分支数)Rule #9 The gain at a selected point s1 on the locus (在某特定点上的根轨迹增益K） Rule #10 The sum of the closed-loop poles (闭环极点 之和） Rule #11 The number of branches of the root locus (根轨迹的分支数）