Either it's patented (and thus disclosed) or it's a trade secret. You cannot have it both ways.
To expand on this a bit, because it's really sad (and bad!) that so many people don't understand the theory behind patents: Encouraging disclosure, and hence reuse, is the point of having a patent system. The word "patent" is latin for "lying open". Patents were created to allow inventors to open their inventions to the world without fear of losing the opportunity to profit from them. Without patents inventors have to keep their ideas secret to profit from them, which impedes progress and adds huge overhead to the process of using the ideas to build things that benefit society.
The fact that InvalidsYnc fails to understand that the notion of an NDA for a patent is utterly nonsensical is sad, but what makes it a big problem is that this lack of understanding isn't actually unreasonable, given how deeply broken our patent system is. It has been subverted and does not accomplish its primary goals of enabling open sharing of ideas.
To understand just how bad it is, note that the way to test whether a patent system is enabling the spread and reuse of good ideas is to examine the way the patent database is used. If the system is functioning well, we should see inventors regularly scouring the patent database in search of ideas they can license in order to solve their problems. If your widget needs to frobnizz cleanly in order to wozzle, but the frobnizzing operation is unreliable and unstable, you should be able to do a patent search for a frobnizz stabilization system which you can license for less that what it would cost you to research your own, which will enable you to bring your wozzling device to market sooner and cheaper.
But in actual practice, at least in the software field and I haven't heard anyone from other fields saying it's different in theirs, attorneys tell working engineers specifically *not* to look at the patent database. This is because it's chock full of obvious ideas which they might independently reinvent, but if the patent holder can prove that the engineer probably saw the patent then it's not just simple infringement due to independent invention, but willful infringement subject to treble damages. In addition, the way in which patents are written means that the database would be extremely hard to use even if engineers did try to mine it. So engineers avoid using the patent database for its intended purpose.
This doesn't mean the patent system is completely failing to do its job, because it undoubtedly still does remove the need for a lot of secrecy, which removes a lot of overhead. But it does mean that it's not working nearly as well as it should. It may be removing some overhead, but it is not actively enabling the reuse of good ideas.