(1) If c1<f (c1)≤c2 (resp.c1≤f (c2)<c2),then f has a single fixed point,a period two orbit,but no points of period greater than two or f has more than one fixed point but no points of other periods,furthermore,if A≠φ and B≠φ,then f (c2)>a (resp.f (c1)<b).
(2) If f (c1)≤c1 (resp.f (c2)≥c2),then f has more than one fixed point,furthermore,if B≠φ and A\{a}≠φ,f (c2)≥a or if a1<f (c2)<a,f2 (c2)>f (c2),(resp.f has more than one fixed point,furthermore,if A≠φ and B\{b}≠φ,f (c1)≤b or if b<f (c2)<b1,f2 (c1)<f (c1)).
(3) If f (c1)>c2 and f (c2)<c1,then f has a single fixed point,a single period two orbit lying in I\(u,v) but no points of period greater than two,where u,v∈[c1,c2] such that f (u)=c2 and f (v)=c1.