If I am not mistaken, you don't have to tell the police that you are carrying when you encounter them, at least in Washington.
Under a casual encounter with an officer you are not required to tell them you are armed, but think of it from their perspective, they walk around our streets everyday in uniform and are literally targeted by everyone on some level, they risk their lives so we can continue to walk around comfortable, consider how many times officers have been targeted and shot at just because they are a cop or because they are doing the job they are paid to do, yes there is always a bad egg in every group someone who will abuse the power they have just because they can, but why make a situation more problematic because you simply do not feel like doing something or just because you can tell them you do not feel you have to follow a request. No you do not have to tell an officer you are armed but why risk startling them or making them unnecessarily uncomfortable, we are not the ones who's lives are targeted everyday for the job we have or the outfit we wear, do a favor to them be kind, cooperative, and intelligent even to those who may not act appropriately right away, it will make a difference and be reciprocated.