In this paper opial's Theorem [1] about the relation between the monotonicity of one-dimensional almost periodic system and the existence of almost periodic solution is generalized. An example in this paper shows that the proof of the same problem given by Fink [2] is a fault.
In this paper we obtain a sufficient and necessary condition for a linear system to have exponential trichotomy and obtain that if a linear system has exponential trichotomy with trichotomy constants α and β, then the roughness of it is .
